CQ. Remove assertErrorsInFile2(), use resolveFilesWithDiagnostics().

Add helpers that resolve non-test files using the same inline diagnostic
expectation format as resolveTestCodeWithDiagnostics.
resolveFileWithDiagnostics handles a single file, while
resolveFilesWithDiagnostics writes all related files before resolving
any of them.

Add multi-file diagnostic expectation generation so context messages in
one file can be referenced from diagnostics reported in another. Teach
expectation updating how to target values in a files-to-code map using
per-entry intra-invocation ids.

Remove assertErrorsInFile2 and migrate diagnostics tests from
hand-written ExpectedError offsets to inline markers. This keeps the
diagnostic range, code, message, and cross-file context next to the code
under test, and makes expectation updates reusable for library and part
tests.

Initialize strong-mode type assertions from resolveFile so callers that
resolve files other than testFile get the same setup.

Change-Id: Ie492155b046c28a535faf21fa9a2e47797caffb0
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/506180
Commit-Queue: Konstantin Shcheglov <scheglov@google.com>
Reviewed-by: Johnni Winther <johnniwinther@google.com>

pkg/analyzer/test/generated/strong_mode_test.dart

@@ -6,6 +6,9 @@ import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/dart/element/nullability_suffix.dart';
 import 'package:analyzer/dart/element/type.dart';
+import 'package:analyzer/dart/element/type_provider.dart';
+import 'package:analyzer/file_system/file_system.dart';
+import 'package:analyzer/src/dart/analysis/results.dart';
 import 'package:analyzer/src/dart/ast/extensions.dart';
 import 'package:analyzer/src/dart/element/type.dart';
 import 'package:analyzer/src/diagnostic/diagnostic.dart' as diag;
@@ -68,37 +71,9 @@ class StrongModeLocalInferenceTest extends PubPackageResolutionTest {
   late final AsserterBuilder<Element, DartType> _hasElement;
 
   @override
-  Future<TestResolvedUnitResult> resolveTestFile() async {
-    var result = await super.resolveTestFile();
-
-    var assertions = _assertions;
-    if (assertions == null) {
-      var typeProvider = result.typeProvider;
-      assertions = _assertions = TypeAssertions(typeProvider);
-      _isType = assertions.isType;
-      _hasElement = assertions.hasElement;
-      _isInstantiationOf = assertions.isInstantiationOf;
-      _isInt = assertions.isInt;
-      _isNever = assertions.isNever;
-      _isNull = assertions.isNull;
-      _isNum = assertions.isNum;
-      _isObject = assertions.isObject;
-      _isString = assertions.isString;
-      _isDynamic = assertions.isDynamic;
-      _isInvalidType = assertions.isInvalidType;
-      _isListOf = assertions.isListOf;
-      _isMapOf = assertions.isMapOf;
-      _isFunction2Of = assertions.isFunction2Of;
-      _isFutureOf = _isInstantiationOf(_hasElement(typeProvider.futureElement));
-      _isFutureOrOf = _isInstantiationOf(
-        _hasElement(typeProvider.futureOrElement),
-      );
-      _isFutureOfDynamic = _isFutureOf([_isDynamic]);
-      _isFutureOfInt = _isFutureOf([_isInt]);
-      _isFutureOfNull = _isFutureOf([_isNull]);
-      _isFutureOrOfInt = _isFutureOrOf([_isInt]);
-    }
-
+  Future<ResolvedUnitResultImpl> resolveFile(File file) async {
+    var result = await super.resolveFile(file);
+    _initAssertions(result.typeProvider);
     return result;
   }
 
@@ -3597,6 +3572,35 @@ class B<T2, U2> {
     );
   }
 
+  void _initAssertions(TypeProvider typeProvider) {
+    var assertions = _assertions;
+    if (assertions == null) {
+      assertions = _assertions = TypeAssertions(typeProvider);
+      _isType = assertions.isType;
+      _hasElement = assertions.hasElement;
+      _isInstantiationOf = assertions.isInstantiationOf;
+      _isInt = assertions.isInt;
+      _isNever = assertions.isNever;
+      _isNull = assertions.isNull;
+      _isNum = assertions.isNum;
+      _isObject = assertions.isObject;
+      _isString = assertions.isString;
+      _isDynamic = assertions.isDynamic;
+      _isInvalidType = assertions.isInvalidType;
+      _isListOf = assertions.isListOf;
+      _isMapOf = assertions.isMapOf;
+      _isFunction2Of = assertions.isFunction2Of;
+      _isFutureOf = _isInstantiationOf(_hasElement(typeProvider.futureElement));
+      _isFutureOrOf = _isInstantiationOf(
+        _hasElement(typeProvider.futureOrElement),
+      );
+      _isFutureOfDynamic = _isFutureOf([_isDynamic]);
+      _isFutureOfInt = _isFutureOf([_isInt]);
+      _isFutureOfNull = _isFutureOf([_isNull]);
+      _isFutureOrOfInt = _isFutureOrOf([_isInt]);
+    }
+  }
+
   /// Helper method for testing `FutureOr<T>`.
   ///
   /// Validates that [code] produces [expectedDiagnostics]. It should define a

pkg/analyzer/test/src/dart/micro/simple_file_resolver_test.dart

@@ -881,15 +881,13 @@ analyzer:
     implicit-casts: true
 ''');
 
-    var aPath = convertPath('/workspace/third_party/dart/aaa/lib/a.dart');
-    await assertErrorsInFile(
-      aPath,
-      r'''
+    var a = getFile('/workspace/third_party/dart/aaa/lib/a.dart');
+    await resolveFileWithDiagnostics(a, r'''
 num a = 0;
 int b = a;
-''',
-      [error(diag.invalidAssignment, 19, 1)],
-    );
+//      ^
+// [diag.invalidAssignment] A value of type 'num' can't be assigned to a variable of type 'int'.
+''');
   }
 
   test_analysisOptions_file_inThirdPartyDartLang() async {
@@ -905,15 +903,13 @@ analyzer:
     implicit-casts: true
 ''');
 
-    var aPath = convertPath('/workspace/third_party/dart_lang/aaa/lib/a.dart');
-    await assertErrorsInFile(
-      aPath,
-      r'''
+    var a = getFile('/workspace/third_party/dart_lang/aaa/lib/a.dart');
+    await resolveFileWithDiagnostics(a, r'''
 num a = 0;
 int b = a;
-''',
-      [error(diag.invalidAssignment, 19, 1)],
-    );
+//      ^
+// [diag.invalidAssignment] A value of type 'num' can't be assigned to a variable of type 'int'.
+''');
   }
 
   test_analysisOptions_lints() async {
@@ -2512,11 +2508,11 @@ void func() {
     newFile('/workspace/dart/aaa/BUILD', '');
     newFile('/workspace/dart/bbb/BUILD', '');
 
-    var aPath = '/workspace/dart/aaa/lib/a.dart';
-    var aResult = await assertErrorsInFile(aPath, '', []);
+    var a = getFile('/workspace/dart/aaa/lib/a.dart');
+    var aResult = await resolveFileWithDiagnostics(a, '');
 
-    var bPath = '/workspace/dart/bbb/lib/a.dart';
-    var bResult = await assertErrorsInFile(bPath, '', []);
+    var b = getFile('/workspace/dart/bbb/lib/a.dart');
+    var bResult = await resolveFileWithDiagnostics(b, '');
 
     // Both files use the same (default) analysis options.
     // So, when we resolve 'bbb', we can reuse the context after 'aaa'.

pkg/analyzer/test/src/dart/resolution/node_text_expectations.dart

@@ -191,6 +191,16 @@ class NodeTextExpectationsCollector {
       methodName: 'assertResolvedNodeText',
       argument: _ArgumentIndex(1),
     ),
+    _AssertMethod(
+      className: 'ResolutionTest',
+      methodName: 'resolveFileWithDiagnostics',
+      argument: _ArgumentIndex(1),
+    ),
+    _AssertMethod(
+      className: 'ResolutionTest',
+      methodName: 'resolveFilesWithDiagnostics',
+      argument: _ArgumentMapEntryValue(mapArgument: _ArgumentIndex(0)),
+    ),
     _AssertMethod(
       className: 'ResolutionTest',
       methodName: 'resolveTestCodeWithDiagnostics',
@@ -239,18 +249,20 @@ class NodeTextExpectationsCollector {
 
   static final Map<String, _File> _files = {};
 
-  static void add(String actual) {
+  static void add(String actual, {String? intraInvocationId}) {
     if (!updatingIsEnabled) {
       return;
     }
 
+    // TODO(scheglov): Use a single mechanism for intra-invocation ids.
+    intraInvocationId ??= NodeTextExpectationsCollector.intraInvocationId;
+
     var traceLines = '${StackTrace.current}'.split('\n');
     for (var assertMethod in assertMethods) {
       // Disambiguate multi-expectation arguments.
       if (assertMethod.argument case _ArgumentNamed namedArgument) {
         if (namedArgument.shouldCheckIntraInvocationId) {
-          var id = NodeTextExpectationsCollector.intraInvocationId;
-          if (namedArgument.name != id) {
+          if (namedArgument.name != intraInvocationId) {
             continue;
           }
         }
@@ -294,7 +306,10 @@ class NodeTextExpectationsCollector {
         }
 
         var argumentList = invocation.argumentList;
-        var argument = assertMethod.argument.get(argumentList);
+        var argument = assertMethod.argument.get(
+          argumentList,
+          intraInvocationId: intraInvocationId,
+        );
         if (argument is! SimpleStringLiteral) {
           fail('Not a literal: ${argument.runtimeType}');
         }
@@ -329,7 +344,7 @@ class UpdateNodeTextExpectations {
 }
 
 sealed class _Argument {
-  Expression get(ArgumentList argumentList);
+  Expression get(ArgumentList argumentList, {String? intraInvocationId});
 }
 
 final class _ArgumentIndex extends _Argument {
@@ -338,7 +353,7 @@ final class _ArgumentIndex extends _Argument {
   _ArgumentIndex(this.index);
 
   @override
-  Expression get(ArgumentList argumentList) {
+  Expression get(ArgumentList argumentList, {String? intraInvocationId}) {
     return argumentList.arguments
         .whereNotType<NamedArgument>()
         .elementAt(index)
@@ -346,6 +361,40 @@ final class _ArgumentIndex extends _Argument {
   }
 }
 
+final class _ArgumentMapEntryValue extends _Argument {
+  final _Argument mapArgument;
+
+  _ArgumentMapEntryValue({required this.mapArgument});
+
+  @override
+  Expression get(ArgumentList argumentList, {String? intraInvocationId}) {
+    if (intraInvocationId == null) {
+      fail('Expected an intra-invocation id for a map entry value.');
+    }
+
+    var index = int.tryParse(intraInvocationId);
+    if (index == null) {
+      fail('Expected a map entry index, got: $intraInvocationId');
+    }
+
+    var mapExpression = mapArgument.get(argumentList);
+    if (mapExpression is! SetOrMapLiteral) {
+      fail('Not a map literal: ${mapExpression.runtimeType}');
+    }
+
+    var elements = mapExpression.elements;
+    if (elements.any((element) => element is! MapLiteralEntry)) {
+      fail('Only plain map literal entries are supported.');
+    }
+
+    if (index < 0 || index >= elements.length) {
+      fail('Map entry index $index is out of range: ${elements.length}');
+    }
+
+    return (elements[index] as MapLiteralEntry).value;
+  }
+}
+
 final class _ArgumentNamed extends _Argument {
   final String name;
   final bool shouldCheckIntraInvocationId;
@@ -353,7 +402,7 @@ final class _ArgumentNamed extends _Argument {
   _ArgumentNamed(this.name, {this.shouldCheckIntraInvocationId = false});
 
   @override
-  Expression get(ArgumentList argumentList) {
+  Expression get(ArgumentList argumentList, {String? intraInvocationId}) {
     return argumentList.arguments
         .whereType<NamedArgument>()
         .where((argument) => argument.name.lexeme == name)

pkg/analyzer/test/src/dart/resolution/resolution.dart

@@ -130,26 +130,6 @@ mixin ResolutionTest implements ResourceProviderMixin {
     return result;
   }
 
-  Future<ResolvedUnitResult> assertErrorsInFile(
-    String path,
-    String content,
-    List<ExpectedDiagnostic> expectedDiagnostics,
-  ) async {
-    var file = newFile(path, content);
-    var result = await resolveFile(file);
-    assertErrorsInResolvedUnit(result, expectedDiagnostics);
-
-    return result;
-  }
-
-  Future<void> assertErrorsInFile2(
-    File file,
-    List<ExpectedDiagnostic> expectedDiagnostics,
-  ) async {
-    var result = await resolveFile(file);
-    assertErrorsInResolvedUnit(result, expectedDiagnostics);
-  }
-
   void assertErrorsInList(
     List<Diagnostic> diagnostics,
     List<ExpectedDiagnostic> expectedDiagnostics,
@@ -414,6 +394,65 @@ mixin ResolutionTest implements ResourceProviderMixin {
     return resolveFile2(file);
   }
 
+  /// Writes all [filesToCode], resolves each file, and checks that each file's
+  /// inline diagnostic markers match its diagnostics.
+  ///
+  /// All files are written before any file is resolved. This supports tests
+  /// where resolving one file cleanly requires related files to already exist,
+  /// such as a library with its parts.
+  Future<Map<File, TestResolvedUnitResult>> resolveFilesWithDiagnostics(
+    Map<File, String> filesToCode,
+  ) async {
+    var files = <({File file, String code, String cleanCode})>[];
+
+    for (var entry in filesToCode.entries) {
+      var cleanCode = removeDiagnosticExpectations(entry.value);
+      modifyFile2(entry.key, cleanCode);
+      files.add((file: entry.key, code: entry.value, cleanCode: cleanCode));
+    }
+
+    var results = <File, TestResolvedUnitResult>{};
+    var diagnosticsByFile = <File, List<Diagnostic>>{};
+
+    for (var file in files) {
+      var result = await resolveFile2(file.file);
+      results[file.file] = result;
+      diagnosticsByFile[file.file] = result.diagnostics;
+    }
+
+    var actualCodeByFile = updateExpectedDiagnosticsForFiles(
+      contentByFile: {for (var file in files) file.file: file.cleanCode},
+      actualDiagnosticsByFile: diagnosticsByFile,
+    );
+
+    var hasMismatch = false;
+    for (var index = 0; index < files.length; index++) {
+      var file = files[index];
+      var actual = actualCodeByFile[file.file]!;
+      if (actual != file.code) {
+        NodeTextExpectationsCollector.add(actual, intraInvocationId: '$index');
+        print('-------- ${file.file.path} --------');
+        printPrettyDiff(file.code, actual);
+        hasMismatch = true;
+      }
+    }
+
+    if (hasMismatch) {
+      fail('See the difference above.');
+    }
+
+    return results;
+  }
+
+  /// Writes [code] to [file], resolves it, and checks that its inline
+  /// diagnostic markers match its diagnostics.
+  Future<TestResolvedUnitResult> resolveFileWithDiagnostics(
+    File file,
+    String code,
+  ) async {
+    return await _resolveFileWithDiagnostics(file, code);
+  }
+
   /// Put the [code] into the test file, and resolve it.
   Future<TestResolvedUnitResult> resolveTestCode(String code) {
     addTestFile(code);
@@ -425,21 +464,7 @@ mixin ResolutionTest implements ResourceProviderMixin {
   Future<TestResolvedUnitResult> resolveTestCodeWithDiagnostics(
     String code,
   ) async {
-    var cleanCode = removeDiagnosticExpectations(code);
-    addTestFile(cleanCode);
-    var result = await resolveTestFile();
-
-    var actual = updateExpectedDiagnostics(
-      content: cleanCode,
-      actualDiagnostics: result.diagnostics,
-    );
-    if (actual != code) {
-      NodeTextExpectationsCollector.add(actual);
-      printPrettyDiff(code, actual);
-      fail('See the difference above.');
-    }
-
-    return result;
+    return await _resolveFileWithDiagnostics(testFile, code);
   }
 
   Future<TestResolvedUnitResult> resolveTestFile() {
@@ -480,6 +505,27 @@ mixin ResolutionTest implements ResourceProviderMixin {
 
     return buffer.toString();
   }
+
+  Future<TestResolvedUnitResult> _resolveFileWithDiagnostics(
+    File file,
+    String code,
+  ) async {
+    var cleanCode = removeDiagnosticExpectations(code);
+    modifyFile2(file, cleanCode);
+    var result = await resolveFile2(file);
+
+    var actual = updateExpectedDiagnostics(
+      content: cleanCode,
+      actualDiagnostics: result.diagnostics,
+    );
+    if (actual != code) {
+      NodeTextExpectationsCollector.add(actual);
+      printPrettyDiff(code, actual);
+      fail('See the difference above.');
+    }
+
+    return result;
+  }
 }
 
 /// A test-facing view of a resolved unit, with utilities derived from it.

pkg/analyzer/test/src/diagnostics/ambiguous_export_test.dart

@@ -2,7 +2,6 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-import 'package:analyzer/src/diagnostic/diagnostic.dart' as diag;
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 
 import '../dart/resolution/context_collection_resolution.dart';
@@ -67,19 +66,21 @@ class N {}
 class N {}
 ''');
 
-    var a = newFile('$testPackageLibPath/a.dart', r'''
+    var a = getFile('$testPackageLibPath/a.dart');
+    var b = getFile('$testPackageLibPath/b.dart');
+
+    await resolveFilesWithDiagnostics({
+      a: r'''
 export 'lib1.dart';
 part 'b.dart';
-''');
-
-    var b = newFile('$testPackageLibPath/b.dart', r'''
+''',
+      b: r'''
 part of 'a.dart';
 export 'lib2.dart';
-''');
-
-    await assertErrorsInFile2(a, []);
-
-    await assertErrorsInFile2(b, [error(diag.ambiguousExport, 25, 11)]);
+//     ^^^^^^^^^^^
+// [diag.ambiguousExport] The name 'N' is defined in the libraries 'package:test/lib1.dart' and 'package:test/lib2.dart'.
+''',
+    });
   }
 
   test_part_part() async {
@@ -91,25 +92,25 @@ class N {}
 class N {}
 ''');
 
-    var a = newFile('$testPackageLibPath/a.dart', r'''
+    var a = getFile('$testPackageLibPath/a.dart');
+    var b = getFile('$testPackageLibPath/b.dart');
+    var c = getFile('$testPackageLibPath/c.dart');
+
+    await resolveFilesWithDiagnostics({
+      a: r'''
 part 'b.dart';
 part 'c.dart';
-''');
-
-    var b = newFile('$testPackageLibPath/b.dart', r'''
+''',
+      b: r'''
 part of 'a.dart';
 export 'lib1.dart';
-''');
-
-    var c = newFile('$testPackageLibPath/c.dart', r'''
+''',
+      c: r'''
 part of 'a.dart';
 export 'lib2.dart';
-''');
-
-    await assertErrorsInFile2(a, []);
-
-    await assertErrorsInFile2(b, []);
-
-    await assertErrorsInFile2(c, [error(diag.ambiguousExport, 25, 11)]);
+//     ^^^^^^^^^^^
+// [diag.ambiguousExport] The name 'N' is defined in the libraries 'package:test/lib1.dart' and 'package:test/lib2.dart'.
+''',
+    });
   }
 }

pkg/analyzer/test/src/diagnostics/assignment_of_do_not_store_test.dart

@@ -222,9 +222,9 @@ abstract class A {
   test_noHintsInTestDir() async {
     // Code that is in a test dir should not trigger the hint.
     // (See:https://github.com/dart-lang/sdk/issues/45594)
-    var result = await resolveFileCode(
-      '$testPackageRootPath/test/test.dart',
-      r'''
+    var file = getFile('$testPackageRootPath/test/test.dart');
+
+    await resolveFileWithDiagnostics(file, r'''
 import 'package:meta/meta.dart';
 
 class A {
@@ -235,9 +235,7 @@ class A {
 class B {
   String f = A().v;
 }
-''',
-    );
-    assertNoErrorsInTestResult(result);
+''');
   }
 
   test_tearOff() async {

pkg/analyzer/test/src/diagnostics/conflicting_field_and_method_test.dart

@@ -2,14 +2,15 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-import 'package:analyzer/src/diagnostic/diagnostic.dart' as diag;
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 
 import '../dart/resolution/context_collection_resolution.dart';
+import '../dart/resolution/node_text_expectations.dart';
 
 main() {
   defineReflectiveSuite(() {
     defineReflectiveTests(ConflictingFieldAndMethodTest);
+    defineReflectiveTests(UpdateNodeTextExpectations);
   });
 }
 
@@ -43,36 +44,22 @@ class B extends A {
 
   @SkippedTest() // TODO(scheglov): implement augmentation
   test_class_inSuper_getter_withAugmentation_inAugmentation() async {
-    var a = newFile('$testPackageLibPath/a.dart', r'''
-part 'b.dart';
-
+    await resolveTestCodeWithDiagnostics(r'''
 class A {
   void foo() {}
 }
 
 class B extends A {}
-''');
-
-    var b = newFile('$testPackageLibPath/b.dart', r'''
-part of 'a.dart';
 
 augment class B {
   int get foo => 0;
 }
 ''');
-
-    await assertErrorsInFile2(a, []);
-
-    await assertErrorsInFile2(b, [
-      error(diag.conflictingFieldAndMethod, 47, 3),
-    ]);
   }
 
   @SkippedTest() // TODO(scheglov): implement augmentation
   test_class_inSuper_getter_withAugmentation_inDeclaration() async {
-    var a = newFile('$testPackageLibPath/a.dart', r'''
-part 'b.dart';
-
+    await resolveTestCodeWithDiagnostics(r'''
 class A {
   void foo() {}
 }
@@ -80,19 +67,9 @@ class A {
 class B {
   int get foo => 0;
 }
-''');
-
-    var b = newFile('$testPackageLibPath/b.dart', r'''
-part of 'a.dart';
 
 augment class B extends A {}
 ''');
-
-    await assertErrorsInFile2(a, [
-      error(diag.conflictingFieldAndMethod, 65, 3),
-    ]);
-
-    await assertErrorsInFile2(b, []);
   }
 
   test_class_inSuper_setter() async {
@@ -140,36 +117,22 @@ enum E with M {
 
   @SkippedTest() // TODO(scheglov): implement augmentation
   test_enum_inMixin_getter_withAugmentation_inAugmentation() async {
-    var a = newFile('$testPackageLibPath/a.dart', r'''
-part 'b.dart';
-
+    await resolveTestCodeWithDiagnostics(r'''
 mixin M {
   void foo() {}
 }
 
 enum E with M {v}
-''');
-
-    var b = newFile('$testPackageLibPath/b.dart', r'''
-part of 'a.dart';
 
 augment enum E {;
   int get foo => 0;
 }
 ''');
-
-    await assertErrorsInFile2(a, []);
-
-    await assertErrorsInFile2(b, [
-      error(diag.conflictingFieldAndMethod, 47, 3),
-    ]);
   }
 
   @SkippedTest() // TODO(scheglov): implement augmentation
   test_enum_inMixin_getter_withAugmentation_inDeclaration() async {
-    var a = newFile('$testPackageLibPath/a.dart', r'''
-part 'b.dart';
-
+    await resolveTestCodeWithDiagnostics(r'''
 mixin M {
   void foo() {}
 }
@@ -178,19 +141,9 @@ enum E {
   v;
   int get foo => 0;
 }
-''');
-
-    var b = newFile('$testPackageLibPath/b.dart', r'''
-part of 'a.dart';
 
 augment enum E with M {}
 ''');
-
-    await assertErrorsInFile2(a, [
-      error(diag.conflictingFieldAndMethod, 69, 3),
-    ]);
-
-    await assertErrorsInFile2(b, []);
   }
 
   test_enum_inMixin_setter() async {
@@ -234,36 +187,22 @@ extension type B(int it) implements A {
 
   @SkippedTest() // TODO(scheglov): implement augmentation
   test_mixin_inSuper_getter_withAugmentation_inAugmentation() async {
-    var a = newFile('$testPackageLibPath/a.dart', r'''
-part 'b.dart';
-
+    await resolveTestCodeWithDiagnostics(r'''
 class A {
   void foo() {}
 }
 
 mixin B on A {}
-''');
-
-    var b = newFile('$testPackageLibPath/b.dart', r'''
-part of 'a.dart';
 
 augment mixin B {
   int get foo => 0;
 }
 ''');
-
-    await assertErrorsInFile2(a, []);
-
-    await assertErrorsInFile2(b, [
-      error(diag.conflictingFieldAndMethod, 47, 3),
-    ]);
   }
 
   @SkippedTest() // TODO(scheglov): implement augmentation
   test_mixin_inSuper_getter_withAugmentation_inDeclaration() async {
-    var a = newFile('$testPackageLibPath/a.dart', r'''
-part 'b.dart';
-
+    await resolveTestCodeWithDiagnostics(r'''
 class A {
   void foo() {}
 }
@@ -271,18 +210,8 @@ class A {
 mixin B {
   int get foo => 0;
 }
-''');
-
-    var b = newFile('$testPackageLibPath/b.dart', r'''
-part of 'a.dart';
 
 augment mixin B on A {}
 ''');
-
-    await assertErrorsInFile2(a, [
-      error(diag.conflictingFieldAndMethod, 65, 3),
-    ]);
-
-    await assertErrorsInFile2(b, []);
   }
 }

pkg/analyzer/test/src/diagnostics/conflicting_generic_interfaces_test.dart

@@ -2,14 +2,15 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-import 'package:analyzer/src/diagnostic/diagnostic.dart' as diag;
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 
 import '../dart/resolution/context_collection_resolution.dart';
+import '../dart/resolution/node_text_expectations.dart';
 
 main() {
   defineReflectiveSuite(() {
     defineReflectiveTests(ConflictingGenericInterfacesTest);
+    defineReflectiveTests(UpdateNodeTextExpectations);
   });
 }
 
@@ -17,25 +18,12 @@ main() {
 class ConflictingGenericInterfacesTest extends PubPackageResolutionTest {
   @SkippedTest() // TODO(scheglov): implement augmentation
   test_class_extends_augmentation_implements() async {
-    var a = newFile('$testPackageLibPath/a.dart', r'''
-part of 'test.dart';
-
-augment class B implements I<String> {}
-''');
-
-    newFile(testFile.path, '''
-part 'a.dart';
-
+    await resolveTestCodeWithDiagnostics('''
 class I<T> {}
 class A implements I<int> {}
 class B extends A {}
+augment class B implements I<String> {}
 ''');
-
-    await assertErrorsInFile2(a, []);
-
-    await assertErrorsInFile2(testFile, [
-      error(diag.conflictingGenericInterfaces, 65, 1),
-    ]);
   }
 
   test_class_extends_implements() async {

pkg/analyzer/test/src/diagnostics/conflicting_method_and_field_test.dart

@@ -2,14 +2,15 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-import 'package:analyzer/src/diagnostic/diagnostic.dart' as diag;
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 
 import '../dart/resolution/context_collection_resolution.dart';
+import '../dart/resolution/node_text_expectations.dart';
 
 main() {
   defineReflectiveSuite(() {
     defineReflectiveTests(ConflictingMethodAndFieldTest);
+    defineReflectiveTests(UpdateNodeTextExpectations);
   });
 }
 
@@ -43,36 +44,22 @@ class B extends A {
 
   @SkippedTest() // TODO(scheglov): implement augmentation
   test_class_inSuper_getter_hasAugmentation_inAugmentation() async {
-    var a = newFile('$testPackageLibPath/a.dart', r'''
-part 'b.dart';
-
+    await resolveTestCodeWithDiagnostics(r'''
 class A {
   int get foo => 0;
 }
 
 class B extends A {}
-''');
-
-    var b = newFile('$testPackageLibPath/b.dart', r'''
-part of 'a.dart';
 
 augment class B {
   void foo() {}
 }
 ''');
-
-    await assertErrorsInFile2(a, []);
-
-    await assertErrorsInFile2(b, [
-      error(diag.conflictingMethodAndField, 44, 3),
-    ]);
   }
 
   @SkippedTest() // TODO(scheglov): implement augmentation
   test_class_inSuper_getter_hasAugmentation_inDeclaration() async {
-    var a = newFile('$testPackageLibPath/a.dart', r'''
-part 'b.dart';
-
+    await resolveTestCodeWithDiagnostics(r'''
 class A {
   int get foo => 0;
 }
@@ -80,19 +67,9 @@ class A {
 class B extends A {
   void foo() {}
 }
-''');
-
-    var b = newFile('$testPackageLibPath/b.dart', r'''
-part of 'a.dart';
 
 augment class B {}
 ''');
-
-    await assertErrorsInFile2(a, [
-      error(diag.conflictingMethodAndField, 76, 3),
-    ]);
-
-    await assertErrorsInFile2(b, []);
   }
 
   test_class_inSuper_setter() async {
@@ -140,36 +117,22 @@ enum E with M {
 
   @SkippedTest() // TODO(scheglov): implement augmentation
   test_enum_inMixin_getter_hasAugmentation_inAugmentation() async {
-    var a = newFile('$testPackageLibPath/a.dart', r'''
-part 'b.dart';
-
+    await resolveTestCodeWithDiagnostics(r'''
 mixin M {
   int get foo => 0;
 }
 
 enum E with M {v}
-''');
-
-    var b = newFile('$testPackageLibPath/b.dart', r'''
-part of 'a.dart';
 
 augment enum E {;
   void foo() {}
 }
 ''');
-
-    await assertErrorsInFile2(a, []);
-
-    await assertErrorsInFile2(b, [
-      error(diag.conflictingMethodAndField, 44, 3),
-    ]);
   }
 
   @SkippedTest() // TODO(scheglov): implement augmentation
   test_enum_inMixin_getter_hasAugmentation_inDeclaration() async {
-    var a = newFile('$testPackageLibPath/a.dart', r'''
-part 'b.dart';
-
+    await resolveTestCodeWithDiagnostics(r'''
 mixin M {
   int get foo => 0;
 }
@@ -178,19 +141,9 @@ enum E with M {
   v;
   void foo() {}
 }
-''');
-
-    var b = newFile('$testPackageLibPath/b.dart', r'''
-part of 'a.dart';
 
 augment enum E {}
 ''');
-
-    await assertErrorsInFile2(a, [
-      error(diag.conflictingMethodAndField, 77, 3),
-    ]);
-
-    await assertErrorsInFile2(b, []);
   }
 
   test_enum_inMixin_setter() async {

pkg/analyzer/test/src/diagnostics/duplicate_definition_test.dart

@@ -3900,24 +3900,22 @@ set f(int value) {}
   }
 
   test_topLevel_setter_setter_inPart() async {
-    var a = newFile('$testPackageLibPath/a.dart', r'''
-part of 'test.dart';
-set f(int value) {}
-''');
+    var a = getFile('$testPackageLibPath/a.dart');
 
-    await resolveTestCodeWithDiagnostics(r'''
+    await resolveFilesWithDiagnostics({
+      testFile: r'''
 part 'a.dart';
 set f(int value) {}
-''');
-
-    await assertErrorsInFile2(a, [
-      error(
-        diag.duplicateDefinition,
-        25,
-        1,
-        contextMessages: [message(testFile, 19, 1)],
-      ),
-    ]);
+//  ^
+// [context 1] The first definition of this name.
+''',
+      a: r'''
+part of 'test.dart';
+set f(int value) {}
+//  ^
+// [diag.duplicateDefinition][context 1] The name 'f=' is already defined.
+''',
+    });
   }
 
   test_typeParameters_class() async {

pkg/analyzer/test/src/diagnostics/duplicate_hidden_name_test.dart

@@ -2,14 +2,15 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-import 'package:analyzer/src/diagnostic/diagnostic.dart' as diag;
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 
 import '../dart/resolution/context_collection_resolution.dart';
+import '../dart/resolution/node_text_expectations.dart';
 
 main() {
   defineReflectiveSuite(() {
     defineReflectiveTests(DuplicateHiddenNameTest);
+    defineReflectiveTests(UpdateNodeTextExpectations);
   });
 }
 
@@ -28,17 +29,19 @@ export 'lib1.dart' hide A, B, A;
   }
 
   test_part_hidden() async {
-    var a = newFile('$testPackageLibPath/a.dart', r'''
-part 'b.dart';
-''');
+    var a = getFile('$testPackageLibPath/a.dart');
+    var b = getFile('$testPackageLibPath/b.dart');
 
-    var b = newFile('$testPackageLibPath/b.dart', r'''
+    await resolveFilesWithDiagnostics({
+      a: r'''
+part 'b.dart';
+''',
+      b: r'''
 part of 'a.dart';
 export 'dart:math' hide pi, Random, pi;
-''');
-
-    await assertErrorsInFile2(a, []);
-
-    await assertErrorsInFile2(b, [error(diag.duplicateHiddenName, 54, 2)]);
+//                                  ^^
+// [diag.duplicateHiddenName] Duplicate hidden name.
+''',
+    });
   }
 }

pkg/analyzer/test/src/diagnostics/duplicate_import_test.dart

@@ -2,15 +2,16 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-import 'package:analyzer/src/diagnostic/diagnostic.dart' as diag;
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 
 import '../dart/resolution/context_collection_resolution.dart';
+import '../dart/resolution/node_text_expectations.dart';
 
 main() {
   defineReflectiveSuite(() {
     defineReflectiveTests(DuplicateExportTest);
     defineReflectiveTests(DuplicateImportTest);
+    defineReflectiveTests(UpdateNodeTextExpectations);
   });
 }
 
@@ -54,19 +55,21 @@ export 'lib1.dart' show A;
   }
 
   test_part_duplicateExport() async {
-    var a = newFile('$testPackageLibPath/a.dart', r'''
-part 'b.dart';
-''');
+    var a = getFile('$testPackageLibPath/a.dart');
+    var b = getFile('$testPackageLibPath/b.dart');
 
-    var b = newFile('$testPackageLibPath/b.dart', r'''
+    await resolveFilesWithDiagnostics({
+      a: r'''
+part 'b.dart';
+''',
+      b: r'''
 part of 'a.dart';
 export 'dart:math';
 export 'dart:math';
-''');
-
-    await assertErrorsInFile2(a, []);
-
-    await assertErrorsInFile2(b, [error(diag.duplicateExport, 45, 11)]);
+//     ^^^^^^^^^^^
+// [diag.duplicateExport] Duplicate export.
+''',
+    });
   }
 }
 
@@ -118,114 +121,119 @@ final a = A();
   }
 
   test_library_importsHaveIdenticalShowHide() async {
-    var lib1 = newFile('$testPackageLibPath/lib1.dart', r'''
+    var lib1 = getFile('$testPackageLibPath/lib1.dart');
+    var lib2 = getFile('$testPackageLibPath/lib2.dart');
+
+    await resolveFileWithDiagnostics(lib1, r'''
 library lib1;
 class A {}
 class B {}
 ''');
 
-    var lib2 = newFile('$testPackageLibPath/lib2.dart', r'''
+    await resolveFileWithDiagnostics(lib2, r'''
 library L;
 import 'lib1.dart' as M show A hide B;
+//                      ^^^^^^^^^^^^^
+// [diag.multipleCombinators] Using multiple 'hide' or 'show' combinators is never necessary and often produces surprising results.
 import 'lib1.dart' as M show A hide B;
+//     ^^^^^^^^^^^
+// [diag.duplicateImport] Duplicate import.
+//                      ^^^^^^^^^^^^^
+// [diag.multipleCombinators] Using multiple 'hide' or 'show' combinators is never necessary and often produces surprising results.
 M.A a = M.A();
 ''');
-
-    await assertErrorsInFile2(lib1, []);
-    await assertErrorsInFile2(lib2, [
-      error(diag.multipleCombinators, 35, 13),
-      error(diag.duplicateImport, 57, 11),
-      error(diag.multipleCombinators, 74, 13),
-    ]);
   }
 
   test_library_oneImportHasHide() async {
-    var lib1 = newFile('$testPackageLibPath/lib1.dart', r'''
+    var lib1 = getFile('$testPackageLibPath/lib1.dart');
+    var lib2 = getFile('$testPackageLibPath/lib2.dart');
+
+    await resolveFileWithDiagnostics(lib1, r'''
 library lib1;
 class A {}
 class B {}''');
 
-    var lib2 = newFile('$testPackageLibPath/lib2.dart', r'''
+    await resolveFileWithDiagnostics(lib2, r'''
 library L;
 import 'lib1.dart';
 import 'lib1.dart' hide A;
 B b = B();
 ''');
-
-    await assertErrorsInFile2(lib1, []);
-    await assertErrorsInFile2(lib2, []);
   }
 
   test_library_oneImportHasShow() async {
-    var lib1 = newFile('$testPackageLibPath/lib1.dart', r'''
+    var lib1 = getFile('$testPackageLibPath/lib1.dart');
+    var lib2 = getFile('$testPackageLibPath/lib2.dart');
+
+    await resolveFileWithDiagnostics(lib1, r'''
 library lib1;
 class A {}
 class B {}
 ''');
 
-    var lib2 = newFile('$testPackageLibPath/lib2.dart', r'''
+    await resolveFileWithDiagnostics(lib2, r'''
 library L;
 import 'lib1.dart';
 import 'lib1.dart' show A; // ignore: unnecessary_import
 A a = A();
 B b = B();
 ''');
-
-    await assertErrorsInFile2(lib1, []);
-    await assertErrorsInFile2(lib2, []);
   }
 
   test_library_oneImportUsesAs() async {
-    var lib1 = newFile('$testPackageLibPath/lib1.dart', r'''
+    var lib1 = getFile('$testPackageLibPath/lib1.dart');
+    var lib2 = getFile('$testPackageLibPath/lib2.dart');
+
+    await resolveFileWithDiagnostics(lib1, r'''
 library lib1;
 class A {}''');
 
-    var lib2 = newFile('$testPackageLibPath/lib2.dart', r'''
+    await resolveFileWithDiagnostics(lib2, r'''
 library L;
 import 'lib1.dart';
 import 'lib1.dart' as one;
 A a = A();
 one.A a2 = one.A();
 ''');
-
-    await assertErrorsInFile2(lib1, []);
-    await assertErrorsInFile2(lib2, []);
   }
 
   test_library_twoDuplicateImports() async {
-    var lib1 = newFile('$testPackageLibPath/lib1.dart', r'''
+    var lib1 = getFile('$testPackageLibPath/lib1.dart');
+    var lib2 = getFile('$testPackageLibPath/lib2.dart');
+
+    await resolveFileWithDiagnostics(lib1, r'''
 library lib1;
 class A {}''');
 
-    var lib2 = newFile('$testPackageLibPath/lib2.dart', r'''
+    await resolveFileWithDiagnostics(lib2, r'''
 library L;
 import 'lib1.dart';
 import 'lib1.dart';
+//     ^^^^^^^^^^^
+// [diag.duplicateImport] Duplicate import.
 import 'lib1.dart';
+//     ^^^^^^^^^^^
+// [diag.duplicateImport] Duplicate import.
 A a = A();
 ''');
-
-    await assertErrorsInFile2(lib1, []);
-    await assertErrorsInFile2(lib2, [
-      error(diag.duplicateImport, 38, 11),
-      error(diag.duplicateImport, 58, 11),
-    ]);
   }
 
   test_part_duplicateImport() async {
-    var a = newFile('$testPackageLibPath/a.dart', r'''
-part 'b.dart';
-''');
+    var a = getFile('$testPackageLibPath/a.dart');
+    var b = getFile('$testPackageLibPath/b.dart');
 
-    var b = newFile('$testPackageLibPath/b.dart', r'''
+    await resolveFilesWithDiagnostics({
+      a: r'''
+part 'b.dart';
+''',
+      b: r'''
 part of 'a.dart';
 import 'dart:math';
 import 'dart:math';
+//     ^^^^^^^^^^^
+// [diag.duplicateImport] Duplicate import.
 void f(Random _) {}
-''');
-
-    await assertErrorsInFile2(a, []);
-
-    await assertErrorsInFile2(b, [error(diag.duplicateImport, 45, 11)]);
+''',
+    });
   }
 }

pkg/analyzer/test/src/diagnostics/duplicate_part_test.dart

@@ -2,14 +2,15 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-import 'package:analyzer/src/diagnostic/diagnostic.dart' as diag;
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 
 import '../dart/resolution/context_collection_resolution.dart';
+import '../dart/resolution/node_text_expectations.dart';
 
 main() {
   defineReflectiveSuite(() {
     defineReflectiveTests(DuplicatePartTest);
+    defineReflectiveTests(UpdateNodeTextExpectations);
   });
 }
 
@@ -57,17 +58,19 @@ part 'part2.dart';
   }
 
   test_part_includesSelf() async {
-    var a = newFile('$testPackageLibPath/a.dart', r'''
-part 'b.dart';
-''');
+    var a = getFile('$testPackageLibPath/a.dart');
+    var b = getFile('$testPackageLibPath/b.dart');
 
-    var b = newFile('$testPackageLibPath/b.dart', r'''
+    await resolveFilesWithDiagnostics({
+      a: r'''
+part 'b.dart';
+''',
+      b: r'''
 part of 'a.dart';
 part 'b.dart';
-''');
-
-    await assertErrorsInFile2(a, []);
-
-    await assertErrorsInFile2(b, [error(diag.duplicatePart, 23, 8)]);
+//   ^^^^^^^^
+// [diag.duplicatePart] The library already contains a part with the URI 'package:test/b.dart'.
+''',
+    });
   }
 }

pkg/analyzer/test/src/diagnostics/duplicate_shown_name_test.dart

@@ -2,14 +2,15 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-import 'package:analyzer/src/diagnostic/diagnostic.dart' as diag;
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 
 import '../dart/resolution/context_collection_resolution.dart';
+import '../dart/resolution/node_text_expectations.dart';
 
 main() {
   defineReflectiveSuite(() {
     defineReflectiveTests(DuplicateShownNameTest);
+    defineReflectiveTests(UpdateNodeTextExpectations);
   });
 }
 
@@ -28,17 +29,19 @@ export 'lib1.dart' show A, B, A;
   }
 
   test_part_shown() async {
-    var a = newFile('$testPackageLibPath/a.dart', r'''
-part 'b.dart';
-''');
+    var a = getFile('$testPackageLibPath/a.dart');
+    var b = getFile('$testPackageLibPath/b.dart');
 
-    var b = newFile('$testPackageLibPath/b.dart', r'''
+    await resolveFilesWithDiagnostics({
+      a: r'''
+part 'b.dart';
+''',
+      b: r'''
 part of 'a.dart';
 export 'dart:math' show pi, Random, pi;
-''');
-
-    await assertErrorsInFile2(a, []);
-
-    await assertErrorsInFile2(b, [error(diag.duplicateShownName, 54, 2)]);
+//                                  ^^
+// [diag.duplicateShownName] Duplicate shown name.
+''',
+    });
   }
 }

pkg/analyzer/test/src/diagnostics/enum_without_constants_test.dart

@@ -2,14 +2,15 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-import 'package:analyzer/src/diagnostic/diagnostic.dart' as diag;
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 
 import '../dart/resolution/context_collection_resolution.dart';
+import '../dart/resolution/node_text_expectations.dart';
 
 main() {
   defineReflectiveSuite(() {
     defineReflectiveTests(EnumWithoutConstantsTest);
+    defineReflectiveTests(UpdateNodeTextExpectations);
   });
 }
 
@@ -17,16 +18,11 @@ main() {
 class EnumWithoutConstantsTest extends PubPackageResolutionTest {
   @SkippedTest() // TODO(scheglov): implement augmentation
   test_hasConstants_inAugmentation() async {
-    newFile('$testPackageLibPath/a.dart', r'''
-part of 'test.dart';
+    await resolveTestCodeWithDiagnostics(r'''
+enum E {}
 augment enum E {
   v
 }
-''');
-
-    await resolveTestCodeWithDiagnostics(r'''
-part 'a.dart';
-enum E {}
 ''');
   }
 
@@ -40,18 +36,9 @@ enum E {}
 
   @SkippedTest() // TODO(scheglov): implement augmentation
   test_noConstants_hasAugmentation() async {
-    var a = newFile('$testPackageLibPath/a.dart', r'''
-part 'b.dart';
+    await resolveTestCodeWithDiagnostics(r'''
 enum E {}
-''');
-
-    var b = newFile('$testPackageLibPath/b.dart', r'''
-part of 'a.dart';
 augment enum E {}
 ''');
-
-    await assertErrorsInFile2(a, [error(diag.enumWithoutConstants, 20, 1)]);
-
-    await assertErrorsInFile2(b, []);
   }
 }

pkg/analyzer/test/src/diagnostics/extends_disallowed_class_test.dart

@@ -2,14 +2,15 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-import 'package:analyzer/src/diagnostic/diagnostic.dart' as diag;
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 
 import '../dart/resolution/context_collection_resolution.dart';
+import '../dart/resolution/node_text_expectations.dart';
 
 main() {
   defineReflectiveSuite(() {
     defineReflectiveTests(ExtendsDisallowedClassTest);
+    defineReflectiveTests(UpdateNodeTextExpectations);
   });
 }
 
@@ -110,18 +111,10 @@ class A extends String {}
 
   @SkippedTest() // TODO(scheglov): implement augmentation
   test_class_String_inAugmentation() async {
-    var a = newFile('$testPackageLibPath/a.dart', r'''
-part 'b.dart';
+    await resolveTestCodeWithDiagnostics(r'''
 class A {}
-''');
-
-    var b = newFile('$testPackageLibPath/b.dart', r'''
-part of 'a.dart';
 augment class A extends String {}
 ''');
-
-    await assertErrorsInFile2(a, []);
-    await assertErrorsInFile2(b, [error(diag.extendsDisallowedClass, 42, 6)]);
   }
 
   test_classTypeAlias_bool() async {

pkg/analyzer/test/src/diagnostics/implements_disallowed_class_test.dart

@@ -2,14 +2,15 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-import 'package:analyzer/src/diagnostic/diagnostic.dart' as diag;
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 
 import '../dart/resolution/context_collection_resolution.dart';
+import '../dart/resolution/node_text_expectations.dart';
 
 main() {
   defineReflectiveSuite(() {
     defineReflectiveTests(ImplementsDisallowedClassTest);
+    defineReflectiveTests(UpdateNodeTextExpectations);
   });
 }
 
@@ -134,20 +135,10 @@ class A implements String {}
 
   @SkippedTest() // TODO(scheglov): implement augmentation
   test_class_String_inAugmentation() async {
-    var a = newFile('$testPackageLibPath/a.dart', r'''
-part 'b.dart';
+    await resolveTestCodeWithDiagnostics(r'''
 class A {}
-''');
-
-    var b = newFile('$testPackageLibPath/b.dart', r'''
-part of 'a.dart';
 augment class A implements String {}
 ''');
-
-    await assertErrorsInFile2(a, []);
-    await assertErrorsInFile2(b, [
-      error(diag.implementsDisallowedClass, 45, 6),
-    ]);
   }
 
   test_class_String_num() async {

pkg/analyzer/test/src/diagnostics/implements_repeated_test.dart

@@ -2,14 +2,15 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-import 'package:analyzer/src/diagnostic/diagnostic.dart' as diag;
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 
 import '../dart/resolution/context_collection_resolution.dart';
+import '../dart/resolution/node_text_expectations.dart';
 
 main() {
   defineReflectiveSuite(() {
     defineReflectiveTests(ImplementsRepeatedTest);
+    defineReflectiveTests(UpdateNodeTextExpectations);
   });
 }
 
@@ -41,22 +42,11 @@ ImplementsClause
 
   @SkippedTest() // TODO(scheglov): implement augmentation
   test_class_implements_2times_augmentation() async {
-    var a = newFile('$testPackageLibPath/a.dart', r'''
-part 'b.dart';
-
+    await resolveTestCodeWithDiagnostics(r'''
 class A {}
 class B implements A {}
-''');
-
-    var b = newFile('$testPackageLibPath/b.dart', r'''
-part of 'a.dart';
-
 augment class B implements A {}
 ''');
-
-    await assertErrorsInFile2(a, []);
-
-    await assertErrorsInFile2(b, [error(diag.implementsRepeated, 46, 1)]);
   }
 
   test_class_implements_2times_viaTypeAlias() async {
@@ -126,22 +116,11 @@ ImplementsClause
 
   @SkippedTest() // TODO(scheglov): implement augmentation
   test_enum_implements_2times_augmentation() async {
-    var a = newFile('$testPackageLibPath/a.dart', r'''
-part 'b.dart';
-
+    await resolveTestCodeWithDiagnostics(r'''
 class A {}
 enum E implements A {v}
-''');
-
-    var b = newFile('$testPackageLibPath/b.dart', r'''
-part of 'a.dart';
-
 augment enum E implements A {}
 ''');
-
-    await assertErrorsInFile2(a, []);
-
-    await assertErrorsInFile2(b, [error(diag.implementsRepeated, 45, 1)]);
   }
 
   test_enum_implements_2times_viaTypeAlias() async {
@@ -212,21 +191,10 @@ ImplementsClause
 
   @SkippedTest() // TODO(scheglov): implement augmentation
   test_extensionType_implements_2times_augmentation() async {
-    var a = newFile('$testPackageLibPath/a.dart', r'''
-part 'b.dart';
-
+    await resolveTestCodeWithDiagnostics(r'''
 extension type A(int it) implements int {}
-''');
-
-    var b = newFile('$testPackageLibPath/b.dart', r'''
-part of 'a.dart';
-
 augment extension type A implements int {}
 ''');
-
-    await assertErrorsInFile2(a, []);
-
-    await assertErrorsInFile2(b, [error(diag.implementsRepeated, 63, 3)]);
   }
 
   test_extensionType_implements_2times_viaTypeAlias() async {
@@ -277,22 +245,11 @@ mixin M implements A, A {}
 
   @SkippedTest() // TODO(scheglov): implement augmentation
   test_mixin_implements_2times_augmentation() async {
-    var a = newFile('$testPackageLibPath/a.dart', r'''
-part 'b.dart';
-
+    await resolveTestCodeWithDiagnostics(r'''
 class A {}
 mixin M implements A {}
-''');
-
-    var b = newFile('$testPackageLibPath/b.dart', r'''
-part of 'a.dart';
-
 augment mixin M implements A {}
 ''');
-
-    await assertErrorsInFile2(a, []);
-
-    await assertErrorsInFile2(b, [error(diag.implementsRepeated, 46, 1)]);
   }
 
   test_mixin_implements_4times() async {

pkg/analyzer/test/src/diagnostics/inconsistent_inheritance_test.dart

@@ -2,21 +2,27 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-import 'package:analyzer/src/diagnostic/diagnostic.dart' as diag;
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 
 import '../dart/resolution/context_collection_resolution.dart';
+import '../dart/resolution/node_text_expectations.dart';
 
 main() {
   defineReflectiveSuite(() {
     defineReflectiveTests(InconsistentInheritanceTest);
+    defineReflectiveTests(UpdateNodeTextExpectations);
   });
 }
 
 @reflectiveTest
 class InconsistentInheritanceTest extends PubPackageResolutionTest {
   test_class_augmentWithInterface_augmentWithMixin() async {
-    var a = newFile('$testPackageLibPath/a.dart', r'''
+    var a = getFile('$testPackageLibPath/a.dart');
+    var b = getFile('$testPackageLibPath/b.dart');
+    var c = getFile('$testPackageLibPath/c.dart');
+
+    await resolveFilesWithDiagnostics({
+      a: r'''
 part 'b.dart';
 part 'c.dart';
 
@@ -29,27 +35,33 @@ abstract class B {
 }
 
 abstract class C extends Object {}
-''');
-
-    var b = newFile('$testPackageLibPath/b.dart', r'''
+//             ^
+// [diag.inconsistentInheritance] Superinterfaces don't have a valid override for 'foo': A.foo (void Function(int)), B.foo (void Function(String)).
+''',
+      b: r'''
 part of 'a.dart';
 
 augment abstract class C implements B {}
-''');
-
-    var c = newFile('$testPackageLibPath/c.dart', r'''
+//                     ^
+// [diag.inconsistentInheritance] Superinterfaces don't have a valid override for 'foo': A.foo (void Function(int)), B.foo (void Function(String)).
+''',
+      c: r'''
 part of 'a.dart';
 
 augment abstract class C with A {}
-''');
-
-    await assertErrorsInFile2(a, [error(diag.inconsistentInheritance, 122, 1)]);
-    await assertErrorsInFile2(b, [error(diag.inconsistentInheritance, 42, 1)]);
-    await assertErrorsInFile2(c, [error(diag.inconsistentInheritance, 42, 1)]);
+//                     ^
+// [diag.inconsistentInheritance] Superinterfaces don't have a valid override for 'foo': A.foo (void Function(int)), B.foo (void Function(String)).
+''',
+    });
   }
 
   test_class_augmentWithMixin_augmentWithInterface() async {
-    var a = newFile('$testPackageLibPath/a.dart', r'''
+    var a = getFile('$testPackageLibPath/a.dart');
+    var b = getFile('$testPackageLibPath/b.dart');
+    var c = getFile('$testPackageLibPath/c.dart');
+
+    await resolveFilesWithDiagnostics({
+      a: r'''
 part 'b.dart';
 part 'c.dart';
 
@@ -62,23 +74,24 @@ abstract class B {
 }
 
 abstract class C extends Object {}
-''');
-
-    var b = newFile('$testPackageLibPath/b.dart', r'''
+//             ^
+// [diag.inconsistentInheritance] Superinterfaces don't have a valid override for 'foo': A.foo (void Function(int)), B.foo (void Function(String)).
+''',
+      b: r'''
 part of 'a.dart';
 
 augment abstract class C with A {}
-''');
-
-    var c = newFile('$testPackageLibPath/c.dart', r'''
+//                     ^
+// [diag.inconsistentInheritance] Superinterfaces don't have a valid override for 'foo': A.foo (void Function(int)), B.foo (void Function(String)).
+''',
+      c: r'''
 part of 'a.dart';
 
 augment abstract class C implements B {}
-''');
-
-    await assertErrorsInFile2(a, [error(diag.inconsistentInheritance, 122, 1)]);
-    await assertErrorsInFile2(b, [error(diag.inconsistentInheritance, 42, 1)]);
-    await assertErrorsInFile2(c, [error(diag.inconsistentInheritance, 42, 1)]);
+//                     ^
+// [diag.inconsistentInheritance] Superinterfaces don't have a valid override for 'foo': A.foo (void Function(int)), B.foo (void Function(String)).
+''',
+    });
   }
 
   test_class_augmentWithMixin_sameFile() async {

pkg/analyzer/test/src/diagnostics/inconsistent_language_version_override_test.dart

@@ -2,193 +2,198 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-import 'package:analyzer/src/diagnostic/diagnostic.dart' as diag;
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 
 import '../dart/resolution/context_collection_resolution.dart';
+import '../dart/resolution/node_text_expectations.dart';
 
 main() {
   defineReflectiveSuite(() {
     defineReflectiveTests(InconsistentLanguageVersionOverrideTest);
+    defineReflectiveTests(UpdateNodeTextExpectations);
   });
 }
 
 @reflectiveTest
 class InconsistentLanguageVersionOverrideTest extends PubPackageResolutionTest {
   test_0_00_000_AAA() async {
-    var a = newFile('$testPackageLibPath/a.dart', r'''
+    var a = getFile('$testPackageLibPath/a.dart');
+    var b = getFile('$testPackageLibPath/b.dart');
+    var c = getFile('$testPackageLibPath/c.dart');
+
+    await resolveFilesWithDiagnostics({
+      a: r'''
 // @dart = 3.10
 part 'b.dart';
-''');
-
-    var b = newFile('$testPackageLibPath/b.dart', r'''
+''',
+      b: r'''
 // @dart = 3.10
 part of 'a.dart';
 part 'c.dart';
-''');
-
-    var c = newFile('$testPackageLibPath/c.dart', r'''
+''',
+      c: r'''
 // @dart = 3.10
 part of 'b.dart';
-''');
-
-    await assertErrorsInFile2(a, []);
-    await assertErrorsInFile2(b, []);
-    await assertErrorsInFile2(c, []);
+''',
+    });
   }
 
   test_0_00_000_AAB() async {
-    var a = newFile('$testPackageLibPath/a.dart', r'''
+    var a = getFile('$testPackageLibPath/a.dart');
+    var b = getFile('$testPackageLibPath/b.dart');
+    var c = getFile('$testPackageLibPath/c.dart');
+
+    await resolveFilesWithDiagnostics({
+      a: r'''
 // @dart = 3.10
 part 'b.dart';
-''');
-
-    var b = newFile('$testPackageLibPath/b.dart', r'''
+''',
+      b: r'''
 // @dart = 3.10
 part of 'a.dart';
 part 'c.dart';
-''');
-
-    var c = newFile('$testPackageLibPath/c.dart', r'''
+//   ^^^^^^^^
+// [diag.inconsistentLanguageVersionOverride] Parts must have exactly the same language version override as the library.
+''',
+      c: r'''
 // @dart = 3.11
 part of 'b.dart';
-''');
-
-    await assertErrorsInFile2(a, []);
-    await assertErrorsInFile2(b, [
-      error(diag.inconsistentLanguageVersionOverride, 39, 8),
-    ]);
-    await assertErrorsInFile2(c, []);
+''',
+    });
   }
 
   test_0_00_000_AAN() async {
-    var a = newFile('$testPackageLibPath/a.dart', r'''
+    var a = getFile('$testPackageLibPath/a.dart');
+    var b = getFile('$testPackageLibPath/b.dart');
+    var c = getFile('$testPackageLibPath/c.dart');
+
+    await resolveFilesWithDiagnostics({
+      a: r'''
 // @dart = 3.10
 part 'b.dart';
-''');
-
-    var b = newFile('$testPackageLibPath/b.dart', r'''
+''',
+      b: r'''
 // @dart = 3.10
 part of 'a.dart';
 part 'c.dart';
-''');
-
-    var c = newFile('$testPackageLibPath/c.dart', r'''
+//   ^^^^^^^^
+// [diag.inconsistentLanguageVersionOverride] Parts must have exactly the same language version override as the library.
+''',
+      c: r'''
 part of 'b.dart';
-''');
-
-    await assertErrorsInFile2(a, []);
-    await assertErrorsInFile2(b, [
-      error(diag.inconsistentLanguageVersionOverride, 39, 8),
-    ]);
-    await assertErrorsInFile2(c, []);
+''',
+    });
   }
 
   test_0_00_000_ABB() async {
-    var a = newFile('$testPackageLibPath/a.dart', r'''
+    var a = getFile('$testPackageLibPath/a.dart');
+    var b = getFile('$testPackageLibPath/b.dart');
+    var c = getFile('$testPackageLibPath/c.dart');
+
+    await resolveFilesWithDiagnostics({
+      a: r'''
 // @dart = 3.10
 part 'b.dart';
-''');
-
-    var b = newFile('$testPackageLibPath/b.dart', r'''
+//   ^^^^^^^^
+// [diag.inconsistentLanguageVersionOverride] Parts must have exactly the same language version override as the library.
+''',
+      b: r'''
 // @dart = 3.11
 part of 'a.dart';
 part 'c.dart';
-''');
-
-    var c = newFile('$testPackageLibPath/c.dart', r'''
+''',
+      c: r'''
 // @dart = 3.11
 part of 'b.dart';
-''');
-
-    await assertErrorsInFile2(a, [
-      error(diag.inconsistentLanguageVersionOverride, 21, 8),
-    ]);
-    await assertErrorsInFile2(b, []);
-    await assertErrorsInFile2(c, []);
+''',
+    });
   }
 
   test_0_00_000_NAA() async {
-    var a = newFile('$testPackageLibPath/a.dart', r'''
-part 'b.dart';
-''');
+    var a = getFile('$testPackageLibPath/a.dart');
+    var b = getFile('$testPackageLibPath/b.dart');
+    var c = getFile('$testPackageLibPath/c.dart');
 
-    var b = newFile('$testPackageLibPath/b.dart', r'''
+    await resolveFilesWithDiagnostics({
+      a: r'''
+part 'b.dart';
+//   ^^^^^^^^
+// [diag.inconsistentLanguageVersionOverride] Parts must have exactly the same language version override as the library.
+''',
+      b: r'''
 // @dart = 3.10
 part of 'a.dart';
 part 'c.dart';
-''');
-
-    var c = newFile('$testPackageLibPath/c.dart', r'''
+''',
+      c: r'''
 // @dart = 3.10
 part of 'b.dart';
-''');
-
-    await assertErrorsInFile2(a, [
-      error(diag.inconsistentLanguageVersionOverride, 5, 8),
-    ]);
-    await assertErrorsInFile2(b, []);
-    await assertErrorsInFile2(c, []);
+''',
+    });
   }
 
   test_0_00_AA() async {
-    var a = newFile('$testPackageLibPath/a.dart', r'''
+    var a = getFile('$testPackageLibPath/a.dart');
+    var b = getFile('$testPackageLibPath/b.dart');
+
+    await resolveFilesWithDiagnostics({
+      a: r'''
 // @dart = 3.2
 part 'b.dart';
-''');
-
-    var b = newFile('$testPackageLibPath/b.dart', r'''
+''',
+      b: r'''
 // @dart = 3.2
 part of 'a.dart';
-''');
-
-    await assertErrorsInFile2(a, []);
-    await assertErrorsInFile2(b, []);
+''',
+    });
   }
 
   test_0_00_AB() async {
-    var a = newFile('$testPackageLibPath/a.dart', r'''
+    var a = getFile('$testPackageLibPath/a.dart');
+    var b = getFile('$testPackageLibPath/b.dart');
+
+    await resolveFilesWithDiagnostics({
+      a: r'''
 // @dart = 3.1
 part 'b.dart';
-''');
-
-    var b = newFile('$testPackageLibPath/b.dart', r'''
+//   ^^^^^^^^
+// [diag.inconsistentLanguageVersionOverride] Parts must have exactly the same language version override as the library.
+''',
+      b: r'''
 // @dart = 3.2
 part of 'a.dart';
-''');
-
-    await assertErrorsInFile2(a, [
-      error(diag.inconsistentLanguageVersionOverride, 20, 8),
-    ]);
-    await assertErrorsInFile2(b, []);
+''',
+    });
   }
 
   test_0_00_NA() async {
-    var a = newFile('$testPackageLibPath/a.dart', r'''
-part 'b.dart';
-''');
+    var a = getFile('$testPackageLibPath/a.dart');
+    var b = getFile('$testPackageLibPath/b.dart');
 
-    var b = newFile('$testPackageLibPath/b.dart', r'''
+    await resolveFilesWithDiagnostics({
+      a: r'''
+part 'b.dart';
+//   ^^^^^^^^
+// [diag.inconsistentLanguageVersionOverride] Parts must have exactly the same language version override as the library.
+''',
+      b: r'''
 // @dart = 3.1
 part of 'a.dart';
-''');
-
-    await assertErrorsInFile2(a, [
-      error(diag.inconsistentLanguageVersionOverride, 5, 8),
-    ]);
-    await assertErrorsInFile2(b, []);
+''',
+    });
   }
 
   test_0_00_NN() async {
-    var a = newFile('$testPackageLibPath/a.dart', r'''
+    var a = getFile('$testPackageLibPath/a.dart');
+    var b = getFile('$testPackageLibPath/b.dart');
+
+    await resolveFilesWithDiagnostics({
+      a: r'''
 part 'b.dart';
-''');
-
-    var b = newFile('$testPackageLibPath/b.dart', r'''
+''',
+      b: r'''
 part of 'a.dart';
-''');
-
-    await assertErrorsInFile2(a, []);
-    await assertErrorsInFile2(b, []);
+''',
+    });
   }
 }

pkg/analyzer/test/src/diagnostics/invalid_do_not_submit_test.dart

@@ -2,14 +2,15 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-import 'package:analyzer/src/diagnostic/diagnostic.dart' as diag;
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 
 import '../dart/resolution/context_collection_resolution.dart';
+import '../dart/resolution/node_text_expectations.dart';
 
 void main() {
   defineReflectiveSuite(() {
     defineReflectiveTests(InvalidDoNotSubmitMemberTest);
+    defineReflectiveTests(UpdateNodeTextExpectations);
   });
 }
 
@@ -25,7 +26,9 @@ class InvalidDoNotSubmitMemberTest extends PubPackageResolutionTest {
   }
 
   test_constructor() async {
-    var a = newFile('$testPackageLibPath/a.dart', r'''
+    var a = getFile('$testPackageLibPath/a.dart');
+    var b = getFile('$testPackageLibPath/b.dart');
+    await resolveFileWithDiagnostics(a, r'''
 import 'package:meta/meta.dart';
 
 class A {
@@ -34,22 +37,21 @@ class A {
 }
 ''');
 
-    var b = newFile('$testPackageLibPath/b.dart', r'''
+    await resolveFileWithDiagnostics(b, r'''
 import 'a.dart';
 
 void b() {
   A();
+//^
+// [diag.invalidUseOfDoNotSubmitMember] Uses of 'A' should not be submitted to source control.
 }
 ''');
-
-    await assertErrorsInFile2(a, []);
-    await assertErrorsInFile2(b, [
-      error(diag.invalidUseOfDoNotSubmitMember, 31, 1),
-    ]);
   }
 
   test_constructor_primary() async {
-    var a = newFile('$testPackageLibPath/a.dart', r'''
+    var a = getFile('$testPackageLibPath/a.dart');
+    var b = getFile('$testPackageLibPath/b.dart');
+    await resolveFileWithDiagnostics(a, r'''
 import 'package:meta/meta.dart';
 
 class A() {
@@ -58,20 +60,19 @@ class A() {
 }
 ''');
 
-    var b = newFile('$testPackageLibPath/b.dart', r'''
+    await resolveFileWithDiagnostics(b, r'''
 import 'a.dart';
 
 var a = A();
+//      ^
+// [diag.invalidUseOfDoNotSubmitMember] Uses of 'A' should not be submitted to source control.
 ''');
-
-    await assertErrorsInFile2(a, []);
-    await assertErrorsInFile2(b, [
-      error(diag.invalidUseOfDoNotSubmitMember, 26, 1),
-    ]);
   }
 
   test_constructorFactory() async {
-    var a = newFile('$testPackageLibPath/a.dart', r'''
+    var a = getFile('$testPackageLibPath/a.dart');
+    var b = getFile('$testPackageLibPath/b.dart');
+    await resolveFileWithDiagnostics(a, r'''
 import 'package:meta/meta.dart';
 
 class A {
@@ -81,29 +82,28 @@ class A {
 }
 ''');
 
-    var b = newFile('$testPackageLibPath/b.dart', r'''
+    await resolveFileWithDiagnostics(b, r'''
 import 'a.dart';
 
 void b() {
   A();
+//^
+// [diag.invalidUseOfDoNotSubmitMember] Uses of 'A' should not be submitted to source control.
 }
 ''');
-
-    await assertErrorsInFile2(a, []);
-    await assertErrorsInFile2(b, [
-      error(diag.invalidUseOfDoNotSubmitMember, 31, 1),
-    ]);
   }
 
   test_exceptionDoNotSubmitMethodReferencingAnotherDoNotSubmitMethod() async {
-    var a = newFile('$testPackageLibPath/a.dart', r'''
+    var a = getFile('$testPackageLibPath/a.dart');
+    var b = getFile('$testPackageLibPath/b.dart');
+    await resolveFileWithDiagnostics(a, r'''
 import 'package:meta/meta.dart';
 
 @doNotSubmit
 void a() {}
 ''');
 
-    var b = newFile('$testPackageLibPath/b.dart', r'''
+    await resolveFileWithDiagnostics(b, r'''
 import 'package:meta/meta.dart';
 
 import 'a.dart';
@@ -124,13 +124,11 @@ void b() {
   }
 }
 ''');
-
-    await assertErrorsInFile2(a, []);
-    await assertErrorsInFile2(b, []);
   }
 
   test_exceptionParameterFromParentFunction() async {
-    var a = newFile('$testPackageLibPath/a.dart', r'''
+    var a = getFile('$testPackageLibPath/a.dart');
+    await resolveFileWithDiagnostics(a, r'''
 import 'package:meta/meta.dart';
 
 void a({@doNotSubmit int? a}) {
@@ -140,24 +138,22 @@ void a({@doNotSubmit int? a}) {
   c();
 }
 ''');
-
-    await assertErrorsInFile2(a, []);
   }
 
   test_exceptionParameterFromSameFunction() async {
-    var a = newFile('$testPackageLibPath/a.dart', r'''
+    var a = getFile('$testPackageLibPath/a.dart');
+    await resolveFileWithDiagnostics(a, r'''
 import 'package:meta/meta.dart';
 
 void a({@doNotSubmit int? a}) {
   print(a);
 }
 ''');
-
-    await assertErrorsInFile2(a, []);
   }
 
   test_exceptionParameterFromSameMethod() async {
-    var a = newFile('$testPackageLibPath/a.dart', r'''
+    var a = getFile('$testPackageLibPath/a.dart');
+    await resolveFileWithDiagnostics(a, r'''
 import 'package:meta/meta.dart';
 
 class A {
@@ -167,12 +163,12 @@ class A {
   }
 }
 ''');
-
-    await assertErrorsInFile2(a, []);
   }
 
   test_extensionGetter() async {
-    var a = newFile('$testPackageLibPath/a.dart', r'''
+    var a = getFile('$testPackageLibPath/a.dart');
+    var b = getFile('$testPackageLibPath/b.dart');
+    await resolveFileWithDiagnostics(a, r'''
 import 'package:meta/meta.dart';
 
 extension A on int {
@@ -181,22 +177,21 @@ extension A on int {
 }
 ''');
 
-    var b = newFile('$testPackageLibPath/b.dart', r'''
+    await resolveFileWithDiagnostics(b, r'''
 import 'a.dart';
 
 void b() {
   print(0.a);
+//        ^
+// [diag.invalidUseOfDoNotSubmitMember] Uses of 'a' should not be submitted to source control.
 }
 ''');
-
-    await assertErrorsInFile2(a, []);
-    await assertErrorsInFile2(b, [
-      error(diag.invalidUseOfDoNotSubmitMember, 39, 1),
-    ]);
   }
 
   test_extensionMethod() async {
-    var a = newFile('$testPackageLibPath/a.dart', r'''
+    var a = getFile('$testPackageLibPath/a.dart');
+    var b = getFile('$testPackageLibPath/b.dart');
+    await resolveFileWithDiagnostics(a, r'''
 import 'package:meta/meta.dart';
 
 extension A on int {
@@ -205,22 +200,21 @@ extension A on int {
 }
 ''');
 
-    var b = newFile('$testPackageLibPath/b.dart', r'''
+    await resolveFileWithDiagnostics(b, r'''
 import 'a.dart';
 
 void b() {
   0.a();
+//  ^
+// [diag.invalidUseOfDoNotSubmitMember] Uses of 'a' should not be submitted to source control.
 }
 ''');
-
-    await assertErrorsInFile2(a, []);
-    await assertErrorsInFile2(b, [
-      error(diag.invalidUseOfDoNotSubmitMember, 33, 1),
-    ]);
   }
 
   test_extensionSetter() async {
-    var a = newFile('$testPackageLibPath/a.dart', r'''
+    var a = getFile('$testPackageLibPath/a.dart');
+    var b = getFile('$testPackageLibPath/b.dart');
+    await resolveFileWithDiagnostics(a, r'''
 import 'package:meta/meta.dart';
 
 extension A on int {
@@ -229,42 +223,40 @@ extension A on int {
 }
 ''');
 
-    var b = newFile('$testPackageLibPath/b.dart', r'''
+    await resolveFileWithDiagnostics(b, r'''
 import 'a.dart';
 
 void b() {
   0.a = 0;
+//  ^
+// [diag.invalidUseOfDoNotSubmitMember] Uses of 'a' should not be submitted to source control.
 }
 ''');
-
-    await assertErrorsInFile2(a, []);
-    await assertErrorsInFile2(b, [
-      error(diag.invalidUseOfDoNotSubmitMember, 33, 1),
-    ]);
   }
 
   test_function() async {
-    var a = newFile('$testPackageLibPath/a.dart', r'''
+    var a = getFile('$testPackageLibPath/a.dart');
+    var b = getFile('$testPackageLibPath/b.dart');
+    await resolveFileWithDiagnostics(a, r'''
 import 'package:meta/meta.dart';
 
 @doNotSubmit
 void a() {}
 ''');
 
-    var b = newFile('$testPackageLibPath/b.dart', r'''
+    await resolveFileWithDiagnostics(b, r'''
 import 'a.dart';
 
 void b() => a();
+//          ^
+// [diag.invalidUseOfDoNotSubmitMember] Uses of 'a' should not be submitted to source control.
 ''');
-
-    await assertErrorsInFile2(a, []);
-    await assertErrorsInFile2(b, [
-      error(diag.invalidUseOfDoNotSubmitMember, 30, 1),
-    ]);
   }
 
   test_getter() async {
-    var a = newFile('$testPackageLibPath/a.dart', r'''
+    var a = getFile('$testPackageLibPath/a.dart');
+    var b = getFile('$testPackageLibPath/b.dart');
+    await resolveFileWithDiagnostics(a, r'''
 import 'package:meta/meta.dart';
 
 class A {
@@ -273,45 +265,44 @@ class A {
 }
 ''');
 
-    var b = newFile('$testPackageLibPath/b.dart', r'''
+    await resolveFileWithDiagnostics(b, r'''
 import 'a.dart';
 
 void b() {
   var a = A();
   print(a.a);
+//        ^
+// [diag.invalidUseOfDoNotSubmitMember] Uses of 'a' should not be submitted to source control.
 }
 ''');
-
-    await assertErrorsInFile2(a, []);
-    await assertErrorsInFile2(b, [
-      error(diag.invalidUseOfDoNotSubmitMember, 54, 1),
-    ]);
   }
 
   test_invalidTargetOfClass() async {
-    var a = newFile('$testPackageLibPath/a.dart', r'''
+    var a = getFile('$testPackageLibPath/a.dart');
+    var b = getFile('$testPackageLibPath/b.dart');
+    await resolveFileWithDiagnostics(a, r'''
 import 'package:meta/meta.dart';
 
 @doNotSubmit
+// [diag.invalidAnnotationTarget][column 2][length 11] The annotation 'doNotSubmit' can only be used on constructors, getters, methods, optional parameters, setters, top-level functions, or top-level variables.
 class A {}
 ''');
 
-    var b = newFile('$testPackageLibPath/b.dart', r'''
+    await resolveFileWithDiagnostics(b, r'''
 import 'a.dart';
 
 void b() {
   A();
+//^
+// [diag.invalidUseOfDoNotSubmitMember] Uses of 'A' should not be submitted to source control.
 }
 ''');
-
-    await assertErrorsInFile2(a, [error(diag.invalidAnnotationTarget, 35, 11)]);
-    await assertErrorsInFile2(b, [
-      error(diag.invalidUseOfDoNotSubmitMember, 31, 1),
-    ]);
   }
 
   test_method() async {
-    var a = newFile('$testPackageLibPath/a.dart', r'''
+    var a = getFile('$testPackageLibPath/a.dart');
+    var b = getFile('$testPackageLibPath/b.dart');
+    await resolveFileWithDiagnostics(a, r'''
 import 'package:meta/meta.dart';
 
 class A {
@@ -320,99 +311,94 @@ class A {
 }
 ''');
 
-    var b = newFile('$testPackageLibPath/b.dart', r'''
+    await resolveFileWithDiagnostics(b, r'''
 import 'a.dart';
 
 void b() {
   var a = A();
   a.a();
+//  ^
+// [diag.invalidUseOfDoNotSubmitMember] Uses of 'a' should not be submitted to source control.
 }
 ''');
-
-    await assertErrorsInFile2(a, []);
-    await assertErrorsInFile2(b, [
-      error(diag.invalidUseOfDoNotSubmitMember, 48, 1),
-    ]);
   }
 
   test_namedParameter() async {
-    var a = newFile('$testPackageLibPath/a.dart', r'''
+    var a = getFile('$testPackageLibPath/a.dart');
+    var b = getFile('$testPackageLibPath/b.dart');
+    await resolveFileWithDiagnostics(a, r'''
 import 'package:meta/meta.dart';
 
 void a({@doNotSubmit int? p}) {}
 ''');
 
-    var b = newFile('$testPackageLibPath/b.dart', r'''
+    await resolveFileWithDiagnostics(b, r'''
 import 'a.dart';
 
 void b() {
   a(p: 0);
+//  ^
+// [diag.invalidUseOfDoNotSubmitMember] Uses of 'p' should not be submitted to source control.
 }
 ''');
-
-    await assertErrorsInFile2(a, []);
-    await assertErrorsInFile2(b, [
-      error(diag.invalidUseOfDoNotSubmitMember, 33, 1),
-    ]);
   }
 
   test_parameter_inPrimaryConstructor() async {
-    var a = newFile('$testPackageLibPath/a.dart', r'''
+    var a = getFile('$testPackageLibPath/a.dart');
+    var b = getFile('$testPackageLibPath/b.dart');
+    await resolveFileWithDiagnostics(a, r'''
 import 'package:meta/meta.dart';
 
 class A([@doNotSubmit int x = 0]);
 ''');
 
-    var b = newFile('$testPackageLibPath/b.dart', r'''
+    await resolveFileWithDiagnostics(b, r'''
 import 'a.dart';
 
 var a = A(1);
+//        ^
+// [diag.invalidUseOfDoNotSubmitMember] Uses of 'x' should not be submitted to source control.
 ''');
-
-    await assertErrorsInFile2(a, []);
-    await assertErrorsInFile2(b, [
-      error(diag.invalidUseOfDoNotSubmitMember, 28, 1),
-    ]);
   }
 
   test_positionalParameter() async {
-    var a = newFile('$testPackageLibPath/a.dart', r'''
+    var a = getFile('$testPackageLibPath/a.dart');
+    var b = getFile('$testPackageLibPath/b.dart');
+    await resolveFileWithDiagnostics(a, r'''
 import 'package:meta/meta.dart';
 
 void a([@doNotSubmit int? p]) {}
 ''');
 
-    var b = newFile('$testPackageLibPath/b.dart', r'''
+    await resolveFileWithDiagnostics(b, r'''
 import 'a.dart';
 
 void b() {
   a(0);
+//  ^
+// [diag.invalidUseOfDoNotSubmitMember] Uses of 'p' should not be submitted to source control.
 }
 ''');
-
-    await assertErrorsInFile2(a, []);
-    await assertErrorsInFile2(b, [
-      error(diag.invalidUseOfDoNotSubmitMember, 33, 1),
-    ]);
   }
 
   test_sameLibrary() async {
-    var a = newFile('$testPackageLibPath/a.dart', r'''
+    var a = getFile('$testPackageLibPath/a.dart');
+    await resolveFileWithDiagnostics(a, r'''
 import 'package:meta/meta.dart';
 
 @doNotSubmit
 void a() {}
 
 void b() => a();
+//          ^
+// [diag.invalidUseOfDoNotSubmitMember] Uses of 'a' should not be submitted to source control.
 ''');
-
-    await assertErrorsInFile2(a, [
-      error(diag.invalidUseOfDoNotSubmitMember, 72, 1),
-    ]);
   }
 
   test_setter() async {
-    var a = newFile('$testPackageLibPath/a.dart', r'''
+    var a = getFile('$testPackageLibPath/a.dart');
+    var b = getFile('$testPackageLibPath/b.dart');
+    await resolveFileWithDiagnostics(a, r'''
 import 'package:meta/meta.dart';
 
 class A {
@@ -421,38 +407,34 @@ class A {
 }
 ''');
 
-    var b = newFile('$testPackageLibPath/b.dart', r'''
+    await resolveFileWithDiagnostics(b, r'''
 import 'a.dart';
 
 void b() {
   var a = A();
   a.a = 0;
+//  ^
+// [diag.invalidUseOfDoNotSubmitMember] Uses of 'a' should not be submitted to source control.
 }
 ''');
-
-    await assertErrorsInFile2(a, []);
-    await assertErrorsInFile2(b, [
-      error(diag.invalidUseOfDoNotSubmitMember, 48, 1),
-    ]);
   }
 
-  test_topLevelVarable() async {
-    var a = newFile('$testPackageLibPath/a.dart', r'''
+  test_topLevelVariable() async {
+    var a = getFile('$testPackageLibPath/a.dart');
+    var b = getFile('$testPackageLibPath/b.dart');
+    await resolveFileWithDiagnostics(a, r'''
 import 'package:meta/meta.dart';
 
 @doNotSubmit
 int a = 0;
 ''');
 
-    var b = newFile('$testPackageLibPath/b.dart', r'''
+    await resolveFileWithDiagnostics(b, r'''
 import 'a.dart';
 
 void b() => print(a);
+//                ^
+// [diag.invalidUseOfDoNotSubmitMember] Uses of 'a' should not be submitted to source control.
 ''');
-
-    await assertErrorsInFile2(a, []);
-    await assertErrorsInFile2(b, [
-      error(diag.invalidUseOfDoNotSubmitMember, 36, 1),
-    ]);
   }
 }

pkg/analyzer/test/src/diagnostics/invalid_override_test.dart

@@ -6,10 +6,12 @@ import 'package:analyzer/src/diagnostic/diagnostic.dart' as diag;
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 
 import '../dart/resolution/context_collection_resolution.dart';
+import '../dart/resolution/node_text_expectations.dart';
 
 main() {
   defineReflectiveSuite(() {
     defineReflectiveTests(InvalidOverrideTest);
+    defineReflectiveTests(UpdateNodeTextExpectations);
   });
 }
 
@@ -31,7 +33,11 @@ abstract class C implements B {
   }
 
   test_class_augment_method_covariant_multiFile_invalid() async {
-    var a = newFile('$testPackageLibPath/a.dart', r'''
+    var a = getFile('$testPackageLibPath/a.dart');
+    var b = getFile('$testPackageLibPath/b.dart');
+
+    await resolveFilesWithDiagnostics({
+      a: r'''
 part 'b.dart';
 
 class A {
@@ -39,22 +45,25 @@ class A {
 }
 
 class B extends A {}
-''');
-
-    var b = newFile('$testPackageLibPath/b.dart', r'''
+''',
+      b: r'''
 part of 'a.dart';
 
 augment class B {
   void foo(covariant String a) {}
+//     ^^^
+// [diag.invalidOverride] 'B.foo' ('void Function(String)') isn't a valid override of 'A.foo' ('void Function(num)').
 }
-''');
-
-    await assertErrorsInFile2(a, []);
-    await assertErrorsInFile2(b, [error(diag.invalidOverride, 44, 3)]);
+''',
+    });
   }
 
   test_class_augment_method_covariant_multiFile_valid() async {
-    var a = newFile('$testPackageLibPath/a.dart', r'''
+    var a = getFile('$testPackageLibPath/a.dart');
+    var b = getFile('$testPackageLibPath/b.dart');
+
+    await resolveFilesWithDiagnostics({
+      a: r'''
 part 'b.dart';
 
 class A {
@@ -62,18 +71,15 @@ class A {
 }
 
 class B extends A {}
-''');
-
-    var b = newFile('$testPackageLibPath/b.dart', r'''
+''',
+      b: r'''
 part of 'a.dart';
 
 augment class B {
   void foo(covariant int a) {}
 }
-''');
-
-    await assertErrorsInFile2(a, []);
-    await assertErrorsInFile2(b, []);
+''',
+    });
   }
 
   test_class_augment_method_covariant_singleFile_invalid() async {
@@ -107,28 +113,31 @@ augment class B {
   }
 
   test_class_augment_method_multiFile() async {
-    var a = newFile('$testPackageLibPath/a.dart', r'''
+    var a = getFile('$testPackageLibPath/a.dart');
+    var b = getFile('$testPackageLibPath/b.dart');
+
+    await resolveFilesWithDiagnostics({
+      a: r'''
 part 'b.dart';
 
 class A {
   int foo() => 0;
+//    ^^^
+// [context 1] The member being overridden.
 }
 
 class B extends A {}
-''');
-
-    var b = newFile('$testPackageLibPath/b.dart', r'''
+''',
+      b: r'''
 part of 'a.dart';
 
 augment class B {
   String foo() => '';
+//       ^^^
+// [diag.invalidOverride][context 1] 'B.foo' ('String Function()') isn't a valid override of 'A.foo' ('int Function()').
 }
-''');
-
-    await assertErrorsInFile2(a, []);
-    await assertErrorsInFile2(b, [
-      error(diag.invalidOverride, 46, 3, contextMessages: [message(a, 32, 3)]),
-    ]);
+''',
+    });
   }
 
   test_class_augment_method_singleFile() async {
@@ -150,33 +159,31 @@ augment class B {
   }
 
   test_class_augment_setter_multiFile() async {
-    var a = newFile('$testPackageLibPath/a.dart', r'''
+    var a = getFile('$testPackageLibPath/a.dart');
+    var b = getFile('$testPackageLibPath/b.dart');
+
+    await resolveFilesWithDiagnostics({
+      a: r'''
 part 'b.dart';
 
 class A {
   void set foo(int value) {}
+//         ^^^
+// [context 1] The setter being overridden.
 }
 
 class B extends A {}
-''');
-
-    var b = newFile('$testPackageLibPath/b.dart', r'''
+''',
+      b: r'''
 part of 'a.dart';
 
 augment class B {
   void set foo(String value) {}
+//         ^^^
+// [diag.invalidOverrideSetter][context 1] The setter 'B.foo' ('void Function(String)') isn't a valid override of 'A.foo' ('void Function(int)').
 }
-''');
-
-    await assertErrorsInFile2(a, []);
-    await assertErrorsInFile2(b, [
-      error(
-        diag.invalidOverrideSetter,
-        48,
-        3,
-        contextMessages: [message(a, 37, 3)],
-      ),
-    ]);
+''',
+    });
   }
 
   test_class_augment_setter_singleFile() async {
@@ -198,7 +205,12 @@ augment class B {
   }
 
   test_class_augment_withClause_multiFile__declaration0_augment1_augment1() async {
-    var a = newFile('$testPackageLibPath/a.dart', r'''
+    var a = getFile('$testPackageLibPath/a.dart');
+    var b = getFile('$testPackageLibPath/b.dart');
+    var c = getFile('$testPackageLibPath/c.dart');
+
+    await resolveFilesWithDiagnostics({
+      a: r'''
 part 'b.dart';
 part 'c.dart';
 
@@ -206,63 +218,60 @@ mixin M1 {}
 mixin M2 {}
 
 class A {}
-''');
-
-    var b = newFile('$testPackageLibPath/b.dart', r'''
+''',
+      b: r'''
 part of 'a.dart';
 
 augment class A with M1 {}
-''');
-
-    var c = newFile('$testPackageLibPath/c.dart', r'''
+''',
+      c: r'''
 part of 'a.dart';
 
 augment class A with M2 {}
-''');
-
-    await assertErrorsInFile2(a, []);
-    await assertErrorsInFile2(b, []);
-    await assertErrorsInFile2(c, []);
+''',
+    });
   }
 
   test_class_augment_withClause_multiFile_declaration0_augment2() async {
-    var a = newFile('$testPackageLibPath/a.dart', r'''
+    var a = getFile('$testPackageLibPath/a.dart');
+    var b = getFile('$testPackageLibPath/b.dart');
+
+    await resolveFilesWithDiagnostics({
+      a: r'''
 part 'b.dart';
 
 mixin M1 {}
 mixin M2 {}
 
 class A {}
-''');
-
-    var b = newFile('$testPackageLibPath/b.dart', r'''
+''',
+      b: r'''
 part of 'a.dart';
 
 augment class A with M1, M2 {}
-''');
-
-    await assertErrorsInFile2(a, []);
-    await assertErrorsInFile2(b, []);
+''',
+    });
   }
 
   test_class_augment_withClause_multiFile_declaration1_augment1() async {
-    var a = newFile('$testPackageLibPath/a.dart', r'''
+    var a = getFile('$testPackageLibPath/a.dart');
+    var b = getFile('$testPackageLibPath/b.dart');
+
+    await resolveFilesWithDiagnostics({
+      a: r'''
 part 'b.dart';
 
 mixin M1 {}
 mixin M2 {}
 
 class A with M1 {}
-''');
-
-    var b = newFile('$testPackageLibPath/b.dart', r'''
+''',
+      b: r'''
 part of 'a.dart';
 
 augment class A with M2 {}
-''');
-
-    await assertErrorsInFile2(a, []);
-    await assertErrorsInFile2(b, []);
+''',
+    });
   }
 
   test_class_augment_withClause_singleFile_declaration0_augment1() async {
@@ -311,22 +320,23 @@ augment class A with M2 {}
   }
 
   test_class_augment_withClause_twoFiles_declaration0_augment1() async {
-    var a = newFile('$testPackageLibPath/a.dart', r'''
+    var a = getFile('$testPackageLibPath/a.dart');
+    var b = getFile('$testPackageLibPath/b.dart');
+
+    await resolveFilesWithDiagnostics({
+      a: r'''
 part 'b.dart';
 
 mixin M {}
 
 class A {}
-''');
-
-    var b = newFile('$testPackageLibPath/b.dart', r'''
+''',
+      b: r'''
 part of 'a.dart';
 
 augment class A with M {}
-''');
-
-    await assertErrorsInFile2(a, []);
-    await assertErrorsInFile2(b, []);
+''',
+    });
   }
 
   test_external_field_covariant_inheritance() async {

pkg/analyzer/test/src/diagnostics/invalid_use_of_protected_member_test.dart

@@ -2,14 +2,15 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-import 'package:analyzer/src/diagnostic/diagnostic.dart' as diag;
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 
 import '../dart/resolution/context_collection_resolution.dart';
+import '../dart/resolution/node_text_expectations.dart';
 
 main() {
   defineReflectiveSuite(() {
     defineReflectiveTests(InvalidUseOfProtectedMemberTest);
+    defineReflectiveTests(UpdateNodeTextExpectations);
   });
 }
 
@@ -22,7 +23,10 @@ class InvalidUseOfProtectedMemberTest extends PubPackageResolutionTest {
   }
 
   test_closure() async {
-    var lib1 = newFile('$testPackageLibPath/lib1.dart', r'''
+    var lib1 = getFile('$testPackageLibPath/lib1.dart');
+    var lib2 = getFile('$testPackageLibPath/lib2.dart');
+
+    await resolveFileWithDiagnostics(lib1, r'''
 import 'package:meta/meta.dart';
 
 class A {
@@ -30,25 +34,17 @@ class A {
   int a() => 42;
 }
 ''');
-    var lib2 = newFile('$testPackageLibPath/lib2.dart', r'''
+
+    await resolveFileWithDiagnostics(lib2, r'''
 import 'lib1.dart';
 
 void main() {
   var leak = new A().a;
+//                   ^
+// [diag.invalidUseOfProtectedMember] The member 'a' can only be used within instance members of subclasses of 'A'.
   print(leak);
 }
 ''');
-
-    await assertErrorsInFile2(lib1, []);
-    await assertErrorsInFile2(lib2, [
-      error(
-        diag.invalidUseOfProtectedMember,
-        56,
-        1,
-        text:
-            "The member 'a' can only be used within instance members of subclasses of 'A'.",
-      ),
-    ]);
   }
 
   test_extendingSubclass() async {
@@ -64,26 +60,27 @@ class B extends A {
   }
 
   test_extension_outsideClassAndFile() async {
-    var lib1 = newFile('$testPackageLibPath/lib1.dart', r'''
+    var lib1 = getFile('$testPackageLibPath/lib1.dart');
+    var lib2 = getFile('$testPackageLibPath/lib2.dart');
+
+    await resolveFileWithDiagnostics(lib1, r'''
 import 'package:meta/meta.dart';
 class A {
   @protected
   void a(int i) {}
 }
 ''');
-    var lib2 = newFile('$testPackageLibPath/lib2.dart', r'''
+
+    await resolveFileWithDiagnostics(lib2, r'''
 import 'lib1.dart';
 extension E on A {
   e() {
     a(7);
+//  ^
+// [diag.invalidUseOfProtectedMember] The member 'a' can only be used within instance members of subclasses of 'A'.
   }
 }
 ''');
-
-    await assertErrorsInFile2(lib1, []);
-    await assertErrorsInFile2(lib2, [
-      error(diag.invalidUseOfProtectedMember, 51, 1),
-    ]);
   }
 
   test_extensionType_implementedMember() async {
@@ -102,7 +99,10 @@ void main() {
   }
 
   test_extensionType_implementedMember_outsideClassAndLibrary() async {
-    var lib1 = newFile('$testPackageLibPath/lib1.dart', r'''
+    var lib1 = getFile('$testPackageLibPath/lib1.dart');
+    var lib2 = getFile('$testPackageLibPath/lib2.dart');
+
+    await resolveFileWithDiagnostics(lib1, r'''
 import 'package:meta/meta.dart';
 class C {
   @protected
@@ -110,16 +110,15 @@ class C {
 }
 extension type E(C c) implements C { }
 ''');
-    var lib2 = newFile('$testPackageLibPath/lib2.dart', r'''
+
+    await resolveFileWithDiagnostics(lib2, r'''
 import 'lib1.dart';
 void main() {
   E(C()).f();
+//       ^
+// [diag.invalidUseOfProtectedMember] The member 'f' can only be used within instance members of subclasses of 'C'.
 }
 ''');
-    await assertErrorsInFile2(lib1, []);
-    await assertErrorsInFile2(lib2, [
-      error(diag.invalidUseOfProtectedMember, 43, 1),
-    ]);
   }
 
   test_extensionType_member() async {
@@ -136,23 +135,25 @@ void main() {
   }
 
   test_extensionType_member_outsideClassAndLibrary() async {
-    var lib1 = newFile('$testPackageLibPath/lib1.dart', r'''
+    var lib1 = getFile('$testPackageLibPath/lib1.dart');
+    var lib2 = getFile('$testPackageLibPath/lib2.dart');
+
+    await resolveFileWithDiagnostics(lib1, r'''
 import 'package:meta/meta.dart';
 extension type E(int i) {
   @protected
   void f(){}
 }
 ''');
-    var lib2 = newFile('$testPackageLibPath/lib2.dart', r'''
+
+    await resolveFileWithDiagnostics(lib2, r'''
 import 'lib1.dart';
 void main() {
   E(1).f();
+//     ^
+// [diag.invalidUseOfProtectedMember] The member 'f' can only be used within instance members of subclasses of 'E'.
 }
 ''');
-    await assertErrorsInFile2(lib1, []);
-    await assertErrorsInFile2(lib2, [
-      error(diag.invalidUseOfProtectedMember, 41, 1),
-    ]);
   }
 
   test_field() async {
@@ -169,42 +170,44 @@ class B extends A {
   }
 
   test_field_outsideClassAndLibrary() async {
-    var lib1 = newFile('$testPackageLibPath/lib1.dart', r'''
+    var lib1 = getFile('$testPackageLibPath/lib1.dart');
+    var lib2 = getFile('$testPackageLibPath/lib2.dart');
+
+    await resolveFileWithDiagnostics(lib1, r'''
 import 'package:meta/meta.dart';
 class A {
   @protected
   int f = 0;
 }
 ''');
-    var lib2 = newFile('$testPackageLibPath/lib2.dart', r'''
+
+    await resolveFileWithDiagnostics(lib2, r'''
 import 'lib1.dart';
 abstract class B {
   int m(A a) => a.f;
+//                ^
+// [diag.invalidUseOfProtectedMember] The member 'f' can only be used within instance members of subclasses of 'A'.
 }
 ''');
-
-    await assertErrorsInFile2(lib1, []);
-    await assertErrorsInFile2(lib2, [
-      error(diag.invalidUseOfProtectedMember, 57, 1),
-    ]);
   }
 
   test_field_outsideClassAndLibrary_originPrimaryConstructor() async {
-    var lib1 = newFile('$testPackageLibPath/lib1.dart', r'''
+    var lib1 = getFile('$testPackageLibPath/lib1.dart');
+    var lib2 = getFile('$testPackageLibPath/lib2.dart');
+
+    await resolveFileWithDiagnostics(lib1, r'''
 import 'package:meta/meta.dart';
 class A(@protected var int f);
 ''');
-    var lib2 = newFile('$testPackageLibPath/lib2.dart', r'''
+
+    await resolveFileWithDiagnostics(lib2, r'''
 import 'lib1.dart';
 abstract class B {
   int m(A a) => a.f;
+//                ^
+// [diag.invalidUseOfProtectedMember] The member 'f' can only be used within instance members of subclasses of 'A'.
 }
 ''');
-
-    await assertErrorsInFile2(lib1, []);
-    await assertErrorsInFile2(lib2, [
-      error(diag.invalidUseOfProtectedMember, 57, 1),
-    ]);
   }
 
   test_field_subclassAndSameLibrary() async {
@@ -220,14 +223,18 @@ abstract class B implements A {
   }
 
   test_fromSuperclassConstraint() async {
-    var lib1 = newFile('$testPackageLibPath/lib1.dart', r'''
+    var lib1 = getFile('$testPackageLibPath/lib1.dart');
+    var lib2 = getFile('$testPackageLibPath/lib2.dart');
+
+    await resolveFileWithDiagnostics(lib1, r'''
 import 'package:meta/meta.dart';
 abstract class A {
   @protected
   void foo() {}
 }
 ''');
-    var lib2 = newFile('$testPackageLibPath/lib2.dart', r'''
+
+    await resolveFileWithDiagnostics(lib2, r'''
 import 'lib1.dart';
 mixin M on A {
   @override
@@ -236,31 +243,29 @@ mixin M on A {
   }
 }
 ''');
-
-    await assertErrorsInFile2(lib1, []);
-    await assertErrorsInFile2(lib2, []);
   }
 
   test_function_outsideClassAndLibrary() async {
-    var lib1 = newFile('$testPackageLibPath/lib1.dart', r'''
+    var lib1 = getFile('$testPackageLibPath/lib1.dart');
+    var lib2 = getFile('$testPackageLibPath/lib2.dart');
+
+    await resolveFileWithDiagnostics(lib1, r'''
 import 'package:meta/meta.dart';
 class A {
   @protected
   void a(){ }
 }
 ''');
-    var lib2 = newFile('$testPackageLibPath/lib2.dart', r'''
+
+    await resolveFileWithDiagnostics(lib2, r'''
 import 'lib1.dart';
 
 main() {
   new A().a();
+//        ^
+// [diag.invalidUseOfProtectedMember] The member 'a' can only be used within instance members of subclasses of 'A'.
 }
 ''');
-
-    await assertErrorsInFile2(lib1, []);
-    await assertErrorsInFile2(lib2, [
-      error(diag.invalidUseOfProtectedMember, 40, 1),
-    ]);
   }
 
   test_function_sameLibrary() async {
@@ -302,48 +307,50 @@ class B extends A {
   }
 
   test_getter_outsideClassAndLibrary() async {
-    var lib1 = newFile('$testPackageLibPath/lib1.dart', r'''
+    var lib1 = getFile('$testPackageLibPath/lib1.dart');
+    var lib2 = getFile('$testPackageLibPath/lib2.dart');
+
+    await resolveFileWithDiagnostics(lib1, r'''
 import 'package:meta/meta.dart';
 class A {
   @protected
   int get a => 42;
 }
 ''');
-    var lib2 = newFile('$testPackageLibPath/lib2.dart', r'''
+
+    await resolveFileWithDiagnostics(lib2, r'''
 import 'lib1.dart';
 class B {
   A a = A();
   int b() => a.a;
+//             ^
+// [diag.invalidUseOfProtectedMember] The member 'a' can only be used within instance members of subclasses of 'A'.
 }
 ''');
-
-    await assertErrorsInFile2(lib1, []);
-    await assertErrorsInFile2(lib2, [
-      error(diag.invalidUseOfProtectedMember, 58, 1),
-    ]);
   }
 
   test_getter_outsideClassAndLibrary_inObjectPattern() async {
-    var lib1 = newFile('$testPackageLibPath/lib1.dart', r'''
+    var lib1 = getFile('$testPackageLibPath/lib1.dart');
+    var lib2 = getFile('$testPackageLibPath/lib2.dart');
+
+    await resolveFileWithDiagnostics(lib1, r'''
 import 'package:meta/meta.dart';
 class A {
   @protected
   int get a => 42;
 }
 ''');
-    var lib2 = newFile('$testPackageLibPath/lib2.dart', r'''
+
+    await resolveFileWithDiagnostics(lib2, r'''
 import 'lib1.dart';
 void f(Object o) {
   switch (o) {
     case A(a: 7): print('yes');
+//         ^
+// [diag.invalidUseOfProtectedMember] The member 'a' can only be used within instance members of subclasses of 'A'.
   }
 }
 ''');
-
-    await assertErrorsInFile2(lib1, []);
-    await assertErrorsInFile2(lib2, [
-      error(diag.invalidUseOfProtectedMember, 65, 1),
-    ]);
   }
 
   test_getter_subclass() async {
@@ -359,7 +366,10 @@ abstract class B implements A {
   }
 
   test_inDocs() async {
-    var lib1 = newFile('$testPackageLibPath/lib1.dart', r'''
+    var lib1 = getFile('$testPackageLibPath/lib1.dart');
+    var lib2 = getFile('$testPackageLibPath/lib2.dart');
+
+    await resolveFileWithDiagnostics(lib1, r'''
 import 'package:meta/meta.dart';
 
 class A {
@@ -373,36 +383,35 @@ class A {
   int a() => 0;
 }
 ''');
-    var lib2 = newFile('$testPackageLibPath/lib2.dart', r'''
+
+    await resolveFileWithDiagnostics(lib2, r'''
 import 'lib1.dart';
 /// OK: [A.a], [A.b], [A.c].
 f() {}
 ''');
-
-    await assertErrorsInFile2(lib1, []);
-    await assertErrorsInFile2(lib2, []);
   }
 
   test_method_outsideClassAndLibrary() async {
-    var lib1 = newFile('$testPackageLibPath/lib1.dart', r'''
+    var lib1 = getFile('$testPackageLibPath/lib1.dart');
+    var lib2 = getFile('$testPackageLibPath/lib2.dart');
+
+    await resolveFileWithDiagnostics(lib1, r'''
 import 'package:meta/meta.dart';
 class A {
   @protected
   void a() {}
 }
 ''');
-    var lib2 = newFile('$testPackageLibPath/lib2.dart', r'''
+
+    await resolveFileWithDiagnostics(lib2, r'''
 import 'lib1.dart';
 
 class B {
   void b() => new A().a();
+//                    ^
+// [diag.invalidUseOfProtectedMember] The member 'a' can only be used within instance members of subclasses of 'A'.
 }
 ''');
-
-    await assertErrorsInFile2(lib1, []);
-    await assertErrorsInFile2(lib2, [
-      error(diag.invalidUseOfProtectedMember, 53, 1),
-    ]);
   }
 
   test_method_subclass() async {
@@ -470,27 +479,28 @@ main() {
     // TODO(srawlins): This test verifies that the analyzer **allows**
     // protected members to be called on objects other than `this`, which
     // violates the protected spec.
-    var lib1 = newFile('$testPackageLibPath/lib1.dart', r'''
+    var lib1 = getFile('$testPackageLibPath/lib1.dart');
+    var lib2 = getFile('$testPackageLibPath/lib2.dart');
+
+    await resolveFileWithDiagnostics(lib1, r'''
 import 'package:meta/meta.dart';
 class A {
   @protected
   void set a(int i) { }
 }
 ''');
-    var lib2 = newFile('$testPackageLibPath/lib2.dart', r'''
+
+    await resolveFileWithDiagnostics(lib2, r'''
 import 'lib1.dart';
 class B {
   A a = A();
   b(int i) {
     a.a = i;
+//    ^
+// [diag.invalidUseOfProtectedMember] The member 'a' can only be used within instance members of subclasses of 'A'.
   }
 }
 ''');
-
-    await assertErrorsInFile2(lib1, []);
-    await assertErrorsInFile2(lib2, [
-      error(diag.invalidUseOfProtectedMember, 62, 1),
-    ]);
   }
 
   test_setter_sameClass() async {

pkg/analyzer/test/src/diagnostics/invalid_use_of_visible_for_template_member_test.dart

@@ -2,15 +2,16 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-import 'package:analyzer/src/diagnostic/diagnostic.dart' as diag;
 import 'package:analyzer_testing/package_config_file_builder.dart';
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 
 import '../dart/resolution/context_collection_resolution.dart';
+import '../dart/resolution/node_text_expectations.dart';
 
 main() {
   defineReflectiveSuite(() {
     defineReflectiveTests(InvalidUseOfVisibleForTemplateMemberTest);
+    defineReflectiveTests(UpdateNodeTextExpectations);
   });
 }
 
@@ -29,76 +30,86 @@ class InvalidUseOfVisibleForTemplateMemberTest
   }
 
   test_class_constructor_named() async {
-    var lib1 = newFile('$testPackageLibPath/lib1.dart', r'''
+    var lib1 = getFile('$testPackageLibPath/lib1.dart');
+    var lib2 = getFile('$testPackageLibPath/lib2.dart');
+
+    await resolveFileWithDiagnostics(lib1, r'''
 import 'package:angular_meta/angular_meta.dart';
 
 class A {
   int _x;
+//    ^^
+// [diag.unusedField] The value of the field '_x' isn't used.
 
   @visibleForTemplate
   A.forTemplate(this._x);
 }
 ''');
-    var lib2 = newFile('$testPackageLibPath/lib2.dart', r'''
+
+    await resolveFileWithDiagnostics(lib2, r'''
 import 'lib1.dart';
 
 void f() {
   new A.forTemplate(0);
+//    ^^^^^^^^^^^^^
+// [diag.invalidUseOfVisibleForTemplateMember] The member 'A.forTemplate' can only be used within 'package:test/lib1.dart' or a template library.
 }
 ''');
-
-    await assertErrorsInFile2(lib1, [error(diag.unusedField, 66, 2)]);
-    await assertErrorsInFile2(lib2, [
-      error(diag.invalidUseOfVisibleForTemplateMember, 38, 13),
-    ]);
   }
 
   test_class_constructor_unnamed() async {
-    var lib1 = newFile('$testPackageLibPath/lib1.dart', r'''
+    var lib1 = getFile('$testPackageLibPath/lib1.dart');
+    var lib2 = getFile('$testPackageLibPath/lib2.dart');
+
+    await resolveFileWithDiagnostics(lib1, r'''
 import 'package:angular_meta/angular_meta.dart';
 
 class A {
   int _x;
+//    ^^
+// [diag.unusedField] The value of the field '_x' isn't used.
 
   @visibleForTemplate
   A(this._x);
 }
 ''');
-    var lib2 = newFile('$testPackageLibPath/lib2.dart', r'''
+
+    await resolveFileWithDiagnostics(lib2, r'''
 import 'lib1.dart';
 
 void f() {
   new A(0);
+//    ^
+// [diag.invalidUseOfVisibleForTemplateMember] The member 'A' can only be used within 'package:test/lib1.dart' or a template library.
 }
 ''');
-
-    await assertErrorsInFile2(lib1, [error(diag.unusedField, 66, 2)]);
-    await assertErrorsInFile2(lib2, [
-      error(diag.invalidUseOfVisibleForTemplateMember, 38, 1),
-    ]);
   }
 
   test_class_declaration() async {
-    var lib1 = newFile('$testPackageLibPath/lib1.dart', r'''
+    var lib1 = getFile('$testPackageLibPath/lib1.dart');
+    var lib2 = getFile('$testPackageLibPath/lib2.dart');
+
+    await resolveFileWithDiagnostics(lib1, r'''
 import 'package:angular_meta/angular_meta.dart';
 
 @visibleForTemplate
 class A {}
 ''');
-    var lib2 = newFile('$testPackageLibPath/lib2.dart', r'''
+
+    await resolveFileWithDiagnostics(lib2, r'''
 import 'lib1.dart';
 
 void f() {
   A;
 }
 ''');
-
-    await assertErrorsInFile2(lib1, []);
-    await assertErrorsInFile2(lib2, []);
   }
 
   test_class_getter() async {
-    var lib1 = newFile('$testPackageLibPath/lib1.dart', r'''
+    var lib1 = getFile('$testPackageLibPath/lib1.dart');
+    var lib2 = getFile('$testPackageLibPath/lib2.dart');
+
+    await resolveFileWithDiagnostics(lib1, r'''
 import 'package:angular_meta/angular_meta.dart';
 
 class A {
@@ -106,22 +117,23 @@ class A {
   int get foo => 7;
 }
 ''');
-    var lib2 = newFile('$testPackageLibPath/lib2.dart', r'''
+
+    await resolveFileWithDiagnostics(lib2, r'''
 import 'lib1.dart';
 
 void f(A a) {
   a.foo;
+//  ^^^
+// [diag.invalidUseOfVisibleForTemplateMember] The member 'foo' can only be used within 'package:test/lib1.dart' or a template library.
 }
 ''');
-
-    await assertErrorsInFile2(lib1, []);
-    await assertErrorsInFile2(lib2, [
-      error(diag.invalidUseOfVisibleForTemplateMember, 39, 3),
-    ]);
   }
 
   test_class_getter_withVisibleOutsideTemplate() async {
-    var lib1 = newFile('$testPackageLibPath/lib1.dart', r'''
+    var lib1 = getFile('$testPackageLibPath/lib1.dart');
+    var lib2 = getFile('$testPackageLibPath/lib2.dart');
+
+    await resolveFileWithDiagnostics(lib1, r'''
 import 'package:angular_meta/angular_meta.dart';
 
 @visibleForTemplate
@@ -133,20 +145,21 @@ class A {
   int get foo => 7;
 }
 ''');
-    var lib2 = newFile('$testPackageLibPath/lib2.dart', r'''
+
+    await resolveFileWithDiagnostics(lib2, r'''
 import 'lib1.dart';
 
 void f(A a) {
   a.foo;
 }
 ''');
-
-    await assertErrorsInFile2(lib1, []);
-    await assertErrorsInFile2(lib2, []);
   }
 
   test_class_method() async {
-    var lib1 = newFile('$testPackageLibPath/lib1.dart', r'''
+    var lib1 = getFile('$testPackageLibPath/lib1.dart');
+    var lib2 = getFile('$testPackageLibPath/lib2.dart');
+
+    await resolveFileWithDiagnostics(lib1, r'''
 import 'package:angular_meta/angular_meta.dart';
 
 @visibleForTemplate
@@ -154,22 +167,23 @@ class A {
   int foo() => 1;
 }
 ''');
-    var lib2 = newFile('$testPackageLibPath/lib2.dart', r'''
+
+    await resolveFileWithDiagnostics(lib2, r'''
 import 'lib1.dart';
 
 void f(A a) {
   a.foo();
+//  ^^^
+// [diag.invalidUseOfVisibleForTemplateMember] The member 'foo' can only be used within 'package:test/lib1.dart' or a template library.
 }
 ''');
-
-    await assertErrorsInFile2(lib1, []);
-    await assertErrorsInFile2(lib2, [
-      error(diag.invalidUseOfVisibleForTemplateMember, 39, 3),
-    ]);
   }
 
   test_class_method_fromTemplate() async {
-    var lib1 = newFile('$testPackageLibPath/lib1.dart', r'''
+    var lib1 = getFile('$testPackageLibPath/lib1.dart');
+    var template = getFile('$testPackageLibPath/lib1.template.dart');
+
+    await resolveFileWithDiagnostics(lib1, r'''
 import 'package:angular_meta/angular_meta.dart';
 
 class A {
@@ -177,20 +191,21 @@ class A {
   void foo() {}
 }
 ''');
-    var template = newFile('$testPackageLibPath/lib1.template.dart', r'''
+
+    await resolveFileWithDiagnostics(template, r'''
 import 'lib1.dart';
 
 class B {
   void b(A a) => a.foo();
 }
 ''');
-
-    await assertErrorsInFile2(lib1, []);
-    await assertErrorsInFile2(template, []);
   }
 
   test_class_method_inMixin() async {
-    var lib1 = newFile('$testPackageLibPath/lib1.dart', r'''
+    var lib1 = getFile('$testPackageLibPath/lib1.dart');
+    var lib2 = getFile('$testPackageLibPath/lib2.dart');
+
+    await resolveFileWithDiagnostics(lib1, r'''
 import 'package:angular_meta/angular_meta.dart';
 
 @visibleForTemplate
@@ -199,22 +214,23 @@ mixin M {
 }
 class C with M {}
 ''');
-    var lib2 = newFile('$testPackageLibPath/lib2.dart', r'''
+
+    await resolveFileWithDiagnostics(lib2, r'''
 import 'lib1.dart';
 
 void f(C c) {
   c.foo();
+//  ^^^
+// [diag.invalidUseOfVisibleForTemplateMember] The member 'foo' can only be used within 'package:test/lib1.dart' or a template library.
 }
 ''');
-
-    await assertErrorsInFile2(lib1, []);
-    await assertErrorsInFile2(lib2, [
-      error(diag.invalidUseOfVisibleForTemplateMember, 39, 3),
-    ]);
   }
 
   test_class_method_inMixin_withVisibleOutsideTemplate() async {
-    var lib1 = newFile('$testPackageLibPath/lib1.dart', r'''
+    var lib1 = getFile('$testPackageLibPath/lib1.dart');
+    var lib2 = getFile('$testPackageLibPath/lib2.dart');
+
+    await resolveFileWithDiagnostics(lib1, r'''
 import 'package:angular_meta/angular_meta.dart';
 
 @visibleForTemplate
@@ -224,20 +240,21 @@ mixin M {
 }
 class C with M {}
 ''');
-    var lib2 = newFile('$testPackageLibPath/lib2.dart', r'''
+
+    await resolveFileWithDiagnostics(lib2, r'''
 import 'lib1.dart';
 
 void f(C c) {
   c.foo();
 }
 ''');
-
-    await assertErrorsInFile2(lib1, []);
-    await assertErrorsInFile2(lib2, []);
   }
 
   test_class_method_parameter_withVisibleOutsideTemplate() async {
-    var lib1 = newFile('$testPackageLibPath/lib1.dart', r'''
+    var lib1 = getFile('$testPackageLibPath/lib1.dart');
+    var lib2 = getFile('$testPackageLibPath/lib2.dart');
+
+    await resolveFileWithDiagnostics(lib1, r'''
 import 'package:angular_meta/angular_meta.dart';
 
 @visibleForTemplate
@@ -250,20 +267,21 @@ class A {
   }
 }
 ''');
-    var lib2 = newFile('$testPackageLibPath/lib2.dart', r'''
+
+    await resolveFileWithDiagnostics(lib2, r'''
 import 'lib1.dart';
 
 void f(A a) {
   a.foo(bar: true);
 }
 ''');
-
-    await assertErrorsInFile2(lib1, []);
-    await assertErrorsInFile2(lib2, []);
   }
 
   test_class_method_withVisibleOutsideTemplate() async {
-    var lib1 = newFile('$testPackageLibPath/lib1.dart', r'''
+    var lib1 = getFile('$testPackageLibPath/lib1.dart');
+    var lib2 = getFile('$testPackageLibPath/lib2.dart');
+
+    await resolveFileWithDiagnostics(lib1, r'''
 import 'package:angular_meta/angular_meta.dart';
 
 @visibleForTemplate
@@ -272,20 +290,21 @@ class A {
   int foo() => 1;
 }
 ''');
-    var lib2 = newFile('$testPackageLibPath/lib2.dart', r'''
+
+    await resolveFileWithDiagnostics(lib2, r'''
 import 'lib1.dart';
 
 void f(A a) {
   a.foo();
 }
 ''');
-
-    await assertErrorsInFile2(lib1, []);
-    await assertErrorsInFile2(lib2, []);
   }
 
   test_class_setter() async {
-    var lib1 = newFile('$testPackageLibPath/lib1.dart', r'''
+    var lib1 = getFile('$testPackageLibPath/lib1.dart');
+    var lib2 = getFile('$testPackageLibPath/lib2.dart');
+
+    await resolveFileWithDiagnostics(lib1, r'''
 import 'package:angular_meta/angular_meta.dart';
 
 @visibleForTemplate
@@ -293,22 +312,23 @@ class A {
   set bar(_) => 7;
 }
 ''');
-    var lib2 = newFile('$testPackageLibPath/lib2.dart', r'''
+
+    await resolveFileWithDiagnostics(lib2, r'''
 import 'lib1.dart';
 
 void f(A a) {
   a.bar = 6;
+//  ^^^
+// [diag.invalidUseOfVisibleForTemplateMember] The member 'bar' can only be used within 'package:test/lib1.dart' or a template library.
 }
 ''');
-
-    await assertErrorsInFile2(lib1, []);
-    await assertErrorsInFile2(lib2, [
-      error(diag.invalidUseOfVisibleForTemplateMember, 39, 3),
-    ]);
   }
 
   test_class_setter_withVisibleOutsideTemplate() async {
-    var lib1 = newFile('$testPackageLibPath/lib1.dart', r'''
+    var lib1 = getFile('$testPackageLibPath/lib1.dart');
+    var lib2 = getFile('$testPackageLibPath/lib2.dart');
+
+    await resolveFileWithDiagnostics(lib1, r'''
 import 'package:angular_meta/angular_meta.dart';
 
 @visibleForTemplate
@@ -317,20 +337,21 @@ class A {
   set bar(_) => 7;
 }
 ''');
-    var lib2 = newFile('$testPackageLibPath/lib2.dart', r'''
+
+    await resolveFileWithDiagnostics(lib2, r'''
 import 'lib1.dart';
 
 void f(A a) {
   a.bar = 6;
 }
 ''');
-
-    await assertErrorsInFile2(lib1, []);
-    await assertErrorsInFile2(lib2, []);
   }
 
   test_enum_constant() async {
-    var lib1 = newFile('$testPackageLibPath/lib1.dart', r'''
+    var lib1 = getFile('$testPackageLibPath/lib1.dart');
+    var lib2 = getFile('$testPackageLibPath/lib2.dart');
+
+    await resolveFileWithDiagnostics(lib1, r'''
 import 'package:angular_meta/angular_meta.dart';
 
 @visibleForTemplate
@@ -339,22 +360,23 @@ enum E {
   b,
 }
 ''');
-    var lib2 = newFile('$testPackageLibPath/lib2.dart', r'''
+
+    await resolveFileWithDiagnostics(lib2, r'''
 import 'lib1.dart';
 
 void f() {
   E.a;
+//  ^
+// [diag.invalidUseOfVisibleForTemplateMember] The member 'a' can only be used within 'package:test/lib1.dart' or a template library.
 }
 ''');
-
-    await assertErrorsInFile2(lib1, []);
-    await assertErrorsInFile2(lib2, [
-      error(diag.invalidUseOfVisibleForTemplateMember, 36, 1),
-    ]);
   }
 
   test_enum_constant_withVisibleOutsideTemplate() async {
-    var lib1 = newFile('$testPackageLibPath/lib1.dart', r'''
+    var lib1 = getFile('$testPackageLibPath/lib1.dart');
+    var lib2 = getFile('$testPackageLibPath/lib2.dart');
+
+    await resolveFileWithDiagnostics(lib1, r'''
 import 'package:angular_meta/angular_meta.dart';
 
 @visibleForTemplate
@@ -364,20 +386,21 @@ enum E {
   b,
 }
 ''');
-    var lib2 = newFile('$testPackageLibPath/lib2.dart', r'''
+
+    await resolveFileWithDiagnostics(lib2, r'''
 import 'lib1.dart';
 
 void f() {
   E.a;
 }
 ''');
-
-    await assertErrorsInFile2(lib1, []);
-    await assertErrorsInFile2(lib2, []);
   }
 
   test_enum_declaration() async {
-    var lib1 = newFile('$testPackageLibPath/lib1.dart', r'''
+    var lib1 = getFile('$testPackageLibPath/lib1.dart');
+    var lib2 = getFile('$testPackageLibPath/lib2.dart');
+
+    await resolveFileWithDiagnostics(lib1, r'''
 import 'package:angular_meta/angular_meta.dart';
 
 @visibleForTemplate
@@ -385,35 +408,37 @@ enum E {
   a,
 }
 ''');
-    var lib2 = newFile('$testPackageLibPath/lib2.dart', r'''
+
+    await resolveFileWithDiagnostics(lib2, r'''
 import 'lib1.dart';
 
 void f() {
   E;
 }
 ''');
-
-    await assertErrorsInFile2(lib1, []);
-    await assertErrorsInFile2(lib2, []);
   }
 
   test_export() async {
-    var lib1 = newFile('$testPackageLibPath/lib1.dart', r'''
+    var lib1 = getFile('$testPackageLibPath/lib1.dart');
+    var lib2 = getFile('$testPackageLibPath/lib2.dart');
+
+    await resolveFileWithDiagnostics(lib1, r'''
 import 'package:angular_meta/angular_meta.dart';
 
 @visibleForTemplate
 int foo() => 1;
 ''');
-    var lib2 = newFile('$testPackageLibPath/lib2.dart', r'''
+
+    await resolveFileWithDiagnostics(lib2, r'''
 export 'lib1.dart' show foo;
 ''');
-
-    await assertErrorsInFile2(lib1, []);
-    await assertErrorsInFile2(lib2, []);
   }
 
   test_extend_class() async {
-    var lib1 = newFile('$testPackageLibPath/lib1.dart', r'''
+    var lib1 = getFile('$testPackageLibPath/lib1.dart');
+    var lib2 = getFile('$testPackageLibPath/lib2.dart');
+
+    await resolveFileWithDiagnostics(lib1, r'''
 import 'package:angular_meta/angular_meta.dart';
 
 @visibleForTemplate
@@ -421,7 +446,8 @@ class A {
   int foo() => 1;
 }
 ''');
-    var lib2 = newFile('$testPackageLibPath/lib2.dart', r'''
+
+    await resolveFileWithDiagnostics(lib2, r'''
 import 'lib1.dart';
 
 class B extends A {
@@ -429,17 +455,17 @@ class B extends A {
 void f() {
   var b = B();
   b.foo();
+//  ^^^
+// [diag.invalidUseOfVisibleForTemplateMember] The member 'foo' can only be used within 'package:test/lib1.dart' or a template library.
 }
 ''');
-
-    await assertErrorsInFile2(lib1, []);
-    await assertErrorsInFile2(lib2, [
-      error(diag.invalidUseOfVisibleForTemplateMember, 73, 3),
-    ]);
   }
 
   test_extend_class_super() async {
-    var lib1 = newFile('$testPackageLibPath/lib1.dart', r'''
+    var lib1 = getFile('$testPackageLibPath/lib1.dart');
+    var lib2 = getFile('$testPackageLibPath/lib2.dart');
+
+    await resolveFileWithDiagnostics(lib1, r'''
 import 'package:angular_meta/angular_meta.dart';
 
 @visibleForTemplate
@@ -447,22 +473,23 @@ class A {
   int foo() => 1;
 }
 ''');
-    var lib2 = newFile('$testPackageLibPath/lib2.dart', r'''
+
+    await resolveFileWithDiagnostics(lib2, r'''
 import 'lib1.dart';
 
 class B extends A {
   void bar() => super.foo();
+//                    ^^^
+// [diag.invalidUseOfVisibleForTemplateMember] The member 'foo' can only be used within 'package:test/lib1.dart' or a template library.
 }
 ''');
-
-    await assertErrorsInFile2(lib1, []);
-    await assertErrorsInFile2(lib2, [
-      error(diag.invalidUseOfVisibleForTemplateMember, 63, 3),
-    ]);
   }
 
   test_extend_class_withOverride() async {
-    var lib1 = newFile('$testPackageLibPath/lib1.dart', r'''
+    var lib1 = getFile('$testPackageLibPath/lib1.dart');
+    var lib2 = getFile('$testPackageLibPath/lib2.dart');
+
+    await resolveFileWithDiagnostics(lib1, r'''
 import 'package:angular_meta/angular_meta.dart';
 
 @visibleForTemplate
@@ -470,7 +497,8 @@ class A {
   int foo() => 1;
 }
 ''');
-    var lib2 = newFile('$testPackageLibPath/lib2.dart', r'''
+
+    await resolveFileWithDiagnostics(lib2, r'''
 import 'lib1.dart';
 
 class B extends A {
@@ -482,13 +510,13 @@ void f() {
   b.foo();
 }
 ''');
-
-    await assertErrorsInFile2(lib1, []);
-    await assertErrorsInFile2(lib2, []);
   }
 
   test_extend_class_withProtected() async {
-    var lib1 = newFile('$testPackageLibPath/lib1.dart', r'''
+    var lib1 = getFile('$testPackageLibPath/lib1.dart');
+    var lib2 = getFile('$testPackageLibPath/lib2.dart');
+
+    await resolveFileWithDiagnostics(lib1, r'''
 import 'package:angular_meta/angular_meta.dart';
 import 'package:meta/meta.dart';
 
@@ -499,7 +527,8 @@ class A {
 }
 
 ''');
-    var lib2 = newFile('$testPackageLibPath/lib2.dart', r'''
+
+    await resolveFileWithDiagnostics(lib2, r'''
 import 'lib1.dart';
 
 class B extends A {
@@ -510,13 +539,13 @@ void f() {
   b.foo();
 }
 ''');
-
-    await assertErrorsInFile2(lib1, []);
-    await assertErrorsInFile2(lib2, []);
   }
 
   test_function_inExtension() async {
-    var lib1 = newFile('$testPackageLibPath/lib1.dart', r'''
+    var lib1 = getFile('$testPackageLibPath/lib1.dart');
+    var lib2 = getFile('$testPackageLibPath/lib2.dart');
+
+    await resolveFileWithDiagnostics(lib1, r'''
 import 'package:angular_meta/angular_meta.dart';
 
 extension E on List {
@@ -524,22 +553,23 @@ extension E on List {
   int foo() => 1;
 }
 ''');
-    var lib2 = newFile('$testPackageLibPath/lib2.dart', r'''
+
+    await resolveFileWithDiagnostics(lib2, r'''
 import 'lib1.dart';
 
 void f() {
   E([]).foo();
+//      ^^^
+// [diag.invalidUseOfVisibleForTemplateMember] The member 'foo' can only be used within 'package:test/lib1.dart' or a template library.
 }
 ''');
-
-    await assertErrorsInFile2(lib1, []);
-    await assertErrorsInFile2(lib2, [
-      error(diag.invalidUseOfVisibleForTemplateMember, 40, 3),
-    ]);
   }
 
   test_function_inExtension_fromTemplate() async {
-    var lib1 = newFile('$testPackageLibPath/lib1.dart', r'''
+    var lib1 = getFile('$testPackageLibPath/lib1.dart');
+    var template = getFile('$testPackageLibPath/lib1.template.dart');
+
+    await resolveFileWithDiagnostics(lib1, r'''
 import 'package:angular_meta/angular_meta.dart';
 
 extension E on List {
@@ -547,20 +577,21 @@ extension E on List {
   int foo() => 1;
 }
 ''');
-    var template = newFile('$testPackageLibPath/lib1.template.dart', r'''
+
+    await resolveFileWithDiagnostics(template, r'''
 import 'lib1.dart';
 
 void f() {
   E([]).foo();
 }
 ''');
-
-    await assertErrorsInFile2(lib1, []);
-    await assertErrorsInFile2(template, []);
   }
 
   test_protectedAndForTemplate_usedAsProtected() async {
-    var lib1 = newFile('$testPackageLibPath/lib1.dart', r'''
+    var lib1 = getFile('$testPackageLibPath/lib1.dart');
+    var lib2 = getFile('$testPackageLibPath/lib2.dart');
+
+    await resolveFileWithDiagnostics(lib1, r'''
 import 'package:angular_meta/angular_meta.dart';
 import 'package:meta/meta.dart';
 
@@ -570,20 +601,21 @@ class A {
   void a(){ }
 }
 ''');
-    var lib2 = newFile('$testPackageLibPath/lib2.dart', r'''
+
+    await resolveFileWithDiagnostics(lib2, r'''
 import 'lib1.dart';
 
 class B extends A {
   void b() => new A().a();
 }
 ''');
-
-    await assertErrorsInFile2(lib1, []);
-    await assertErrorsInFile2(lib2, []);
   }
 
   test_protectedAndForTemplate_usedAsTemplate() async {
-    var lib1 = newFile('$testPackageLibPath/lib1.dart', r'''
+    var lib1 = getFile('$testPackageLibPath/lib1.dart');
+    var template = getFile('$testPackageLibPath/lib1.template.dart');
+
+    await resolveFileWithDiagnostics(lib1, r'''
 import 'package:angular_meta/angular_meta.dart';
 import 'package:meta/meta.dart';
 
@@ -593,20 +625,21 @@ class A {
   void foo() {}
 }
 ''');
-    var template = newFile('$testPackageLibPath/lib1.template.dart', r'''
+
+    await resolveFileWithDiagnostics(template, r'''
 import 'lib1.dart';
 
 void f(A a) {
   a.foo();
 }
 ''');
-
-    await assertErrorsInFile2(lib1, []);
-    await assertErrorsInFile2(template, []);
   }
 
   test_static_class_member_withVisibleOutsideTemplate() async {
-    var lib1 = newFile('$testPackageLibPath/lib1.dart', r'''
+    var lib1 = getFile('$testPackageLibPath/lib1.dart');
+    var lib2 = getFile('$testPackageLibPath/lib2.dart');
+
+    await resolveFileWithDiagnostics(lib1, r'''
 import 'package:angular_meta/angular_meta.dart';
 
 @visibleForTemplate
@@ -615,77 +648,78 @@ class C {
   static int foo() => 1;
 }
 ''');
-    var lib2 = newFile('$testPackageLibPath/lib2.dart', r'''
+
+    await resolveFileWithDiagnostics(lib2, r'''
 import 'lib1.dart';
 
 void f() {
   C.foo();
 }
 ''');
-
-    await assertErrorsInFile2(lib1, []);
-    await assertErrorsInFile2(lib2, []);
   }
 
   test_supertype_method() async {
-    var lib1 = newFile('$testPackageLibPath/lib1.dart', r'''
+    var lib1 = getFile('$testPackageLibPath/lib1.dart');
+    var lib2 = getFile('$testPackageLibPath/lib2.dart');
+
+    await resolveFileWithDiagnostics(lib1, r'''
 import 'package:angular_meta/angular_meta.dart';
 
 @visibleForTemplate
 class A {}
 var a = A();
 ''');
-    var lib2 = newFile('$testPackageLibPath/lib2.dart', r'''
+
+    await resolveFileWithDiagnostics(lib2, r'''
 import 'lib1.dart';
 
 void f() {
   print(a.hashCode);
 }
 ''');
-
-    await assertErrorsInFile2(lib1, []);
-    await assertErrorsInFile2(lib2, []);
   }
 
   test_topLevelFunction() async {
-    var lib1 = newFile('$testPackageLibPath/lib1.dart', r'''
+    var lib1 = getFile('$testPackageLibPath/lib1.dart');
+    var lib2 = getFile('$testPackageLibPath/lib2.dart');
+
+    await resolveFileWithDiagnostics(lib1, r'''
 import 'package:angular_meta/angular_meta.dart';
 
 @visibleForTemplate
 int foo() => 1;
 ''');
-    var lib2 = newFile('$testPackageLibPath/lib2.dart', r'''
+
+    await resolveFileWithDiagnostics(lib2, r'''
 import 'lib1.dart';
 
 void f() {
   foo();
+//^^^
+// [diag.invalidUseOfVisibleForTemplateMember] The member 'foo' can only be used within 'package:test/lib1.dart' or a template library.
 }
 ''');
-
-    await assertErrorsInFile2(lib1, []);
-    await assertErrorsInFile2(lib2, [
-      error(diag.invalidUseOfVisibleForTemplateMember, 34, 3),
-    ]);
   }
 
   test_topLevelVariable() async {
-    var lib1 = newFile('$testPackageLibPath/lib1.dart', r'''
+    var lib1 = getFile('$testPackageLibPath/lib1.dart');
+    var lib2 = getFile('$testPackageLibPath/lib2.dart');
+
+    await resolveFileWithDiagnostics(lib1, r'''
 import 'package:angular_meta/angular_meta.dart';
 
 @visibleForTemplate
 int foo = 7;
 ''');
-    var lib2 = newFile('$testPackageLibPath/lib2.dart', r'''
+
+    await resolveFileWithDiagnostics(lib2, r'''
 import 'lib1.dart';
 
 void f() {
   foo;
+//^^^
+// [diag.invalidUseOfVisibleForTemplateMember] The member 'foo' can only be used within 'package:test/lib1.dart' or a template library.
 }
 ''');
-
-    await assertErrorsInFile2(lib1, []);
-    await assertErrorsInFile2(lib2, [
-      error(diag.invalidUseOfVisibleForTemplateMember, 34, 3),
-    ]);
   }
 }

pkg/analyzer/test/src/diagnostics/invalid_use_of_visible_for_testing_member_test.dart

@@ -2,10 +2,10 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-import 'package:analyzer/src/diagnostic/diagnostic.dart' as diag;
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 
 import '../dart/resolution/context_collection_resolution.dart';
+import '../dart/resolution/node_text_expectations.dart';
 
 main() {
   defineReflectiveSuite(() {
@@ -13,6 +13,7 @@ main() {
     defineReflectiveTests(
       InvalidUseOfVisibleForTestingMemberWithTestInAncestorPathTest,
     );
+    defineReflectiveTests(UpdateNodeTextExpectations);
   });
 }
 
@@ -84,12 +85,12 @@ class A {
   void a() {}
 }
 ''');
-    var test = newFile('$testPackageRootPath/integration_test/test.dart', r'''
+
+    var file = getFile('$testPackageRootPath/integration_test/test.dart');
+    await resolveFileWithDiagnostics(file, r'''
 import 'package:test/lib1.dart';
 void f() => A().a();
 ''');
-
-    await assertErrorsInFile2(test, []);
   }
 
   test_fromTestDirectory() async {
@@ -100,12 +101,12 @@ class A {
   void a() {}
 }
 ''');
-    var test = newFile('$testPackageRootPath/test/test.dart', r'''
+
+    var file = getFile('$testPackageRootPath/test/test.dart');
+    await resolveFileWithDiagnostics(file, r'''
 import 'package:test/lib1.dart';
 void f() => A().a();
 ''');
-
-    await assertErrorsInFile2(test, []);
   }
 
   test_fromTestDriverDirectory() async {
@@ -116,12 +117,12 @@ class A {
   void a() {}
 }
 ''');
-    var test = newFile('$testPackageRootPath/test_driver/test.dart', r'''
+
+    var file = getFile('$testPackageRootPath/test_driver/test.dart');
+    await resolveFileWithDiagnostics(file, r'''
 import 'package:test/lib1.dart';
 void f() => A().a();
 ''');
-
-    await assertErrorsInFile2(test, []);
   }
 
   test_fromTestingDirectory() async {
@@ -132,12 +133,12 @@ class A {
   void a() {}
 }
 ''');
-    var lib2 = newFile('$testPackageRootPath/testing/lib2.dart', r'''
+
+    var lib2 = getFile('$testPackageRootPath/testing/lib2.dart');
+    await resolveFileWithDiagnostics(lib2, r'''
 import 'package:test/lib1.dart';
 void f() => A().a();
 ''');
-
-    await assertErrorsInFile2(lib2, []);
   }
 
   test_functionInExtension() async {
@@ -166,14 +167,14 @@ extension E on List {
   int m() => 1;
 }
 ''');
-    var test = newFile('$testPackageRootPath/test/test.dart', r'''
+
+    var file = getFile('$testPackageRootPath/test/test.dart');
+    await resolveFileWithDiagnostics(file, r'''
 import 'package:test/lib1.dart';
 void f() {
   E([]).m();
 }
 ''');
-
-    await assertErrorsInFile2(test, []);
   }
 
   test_getter() async {
@@ -202,18 +203,18 @@ class A {
   int get g => 7;
 }
 ''');
-    var lib2 = newFile('$testPackageLibPath/lib2.dart', r'''
+
+    var lib2 = getFile('$testPackageLibPath/lib2.dart');
+    await resolveFileWithDiagnostics(lib2, r'''
 import 'lib1.dart';
 void f(Object o) {
   switch (o) {
     case A(g: 7): print('yes');
+//         ^
+// [diag.invalidUseOfVisibleForTestingMember] The member 'g' can only be used within 'package:test/lib1.dart' or a test.
   }
 }
 ''');
-
-    await assertErrorsInFile2(lib2, [
-      error(diag.invalidUseOfVisibleForTestingMember, 65, 1),
-    ]);
   }
 
   test_import_hide() async {
@@ -317,14 +318,13 @@ extension type E(int i) {
 }
 ''');
 
-    var test = newFile('$testPackageRootPath/test/test.dart', r'''
+    var file = getFile('$testPackageRootPath/test/test.dart');
+    await resolveFileWithDiagnostics(file, r'''
 import 'package:test/lib1.dart';
 void f() {
   E(1).m();
 }
 ''');
-
-    await assertErrorsInFile2(test, []);
   }
 
   test_mixin() async {
@@ -393,14 +393,13 @@ class A {
 }
 ''');
 
-    var test = newFile('$testPackageRootPath/test/test.dart', r'''
+    var file = getFile('$testPackageRootPath/test/test.dart');
+    await resolveFileWithDiagnostics(file, r'''
 import 'package:test/lib1.dart';
 void f() {
   A().a();
 }
 ''');
-
-    await assertErrorsInFile2(test, []);
   }
 
   test_setter() async {

pkg/analyzer/test/src/diagnostics/mixin_of_disallowed_class_test.dart

@@ -79,18 +79,10 @@ class A extends Object with int {}
 
   @SkippedTest() // TODO(scheglov): implement augmentation
   test_class_int_inAugmentation() async {
-    var a = newFile('$testPackageLibPath/a.dart', r'''
-part 'b.dart';
+    await resolveTestCodeWithDiagnostics(r'''
 class A {}
-''');
-
-    var b = newFile('$testPackageLibPath/b.dart', r'''
-part of 'a.dart';
 augment class A with int {}
 ''');
-
-    await assertErrorsInFile2(a, []);
-    await assertErrorsInFile2(b, []);
   }
 
   test_class_Null() async {
@@ -212,17 +204,9 @@ enum E with int {
 
   @SkippedTest() // TODO(scheglov): implement augmentation
   test_enum_int_inAugmentation() async {
-    var a = newFile('$testPackageLibPath/a.dart', r'''
-part 'b.dart';
+    await resolveTestCodeWithDiagnostics(r'''
 enum A {v}
-''');
-
-    var b = newFile('$testPackageLibPath/b.dart', r'''
-part of 'a.dart';
 augment enum A with int {}
 ''');
-
-    await assertErrorsInFile2(a, []);
-    await assertErrorsInFile2(b, []);
   }
 }

pkg/analyzer/test/src/diagnostics/mixin_super_class_constraint_disallowed_class_test.dart

@@ -45,18 +45,10 @@ MixinOnClause
 
   @SkippedTest() // TODO(scheglov): implement augmentation
   test_in_inAugmentation() async {
-    var a = newFile('$testPackageLibPath/a.dart', r'''
-part 'b.dart';
+    await resolveTestCodeWithDiagnostics(r'''
 mixin A {}
-''');
-
-    var b = newFile('$testPackageLibPath/b.dart', r'''
-part of 'a.dart';
 augment mixin A on int {}
 ''');
-
-    await assertErrorsInFile2(a, []);
-    await assertErrorsInFile2(b, []);
   }
 
   test_int() async {

pkg/analyzer/test/src/diagnostics/non_abstract_class_inherits_abstract_member_test.dart

@@ -2,7 +2,6 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-import 'package:analyzer/src/diagnostic/diagnostic.dart' as diag;
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 
 import '../dart/resolution/context_collection_resolution.dart';
@@ -126,7 +125,11 @@ class C extends B {}
   }
 
   test_augment_withClause_crossFile_error_nonAbstractClassInheritsAbstractMember() async {
-    var a = newFile('$testPackageLibPath/a.dart', r'''
+    var a = getFile('$testPackageLibPath/a.dart');
+    var b = getFile('$testPackageLibPath/b.dart');
+
+    await resolveFilesWithDiagnostics({
+      a: r'''
 part 'b.dart';
 
 mixin M {
@@ -134,20 +137,17 @@ mixin M {
 }
 
 class A {}
-''');
-
-    var b = newFile('$testPackageLibPath/b.dart', r'''
+//    ^
+// [diag.nonAbstractClassInheritsAbstractMemberOne] Missing concrete implementation of 'M.foo'.
+''',
+      b: r'''
 part of 'a.dart';
 
 augment class A with M {}
-''');
-
-    await assertErrorsInFile2(a, [
-      error(diag.nonAbstractClassInheritsAbstractMemberOne, 48, 1),
-    ]);
-    await assertErrorsInFile2(b, [
-      error(diag.nonAbstractClassInheritsAbstractMemberOne, 33, 1),
-    ]);
+//            ^
+// [diag.nonAbstractClassInheritsAbstractMemberOne] Missing concrete implementation of 'M.foo'.
+''',
+    });
   }
 
   test_augment_withClause_sameFile_error_nonAbstractClassInheritsAbstractMember() async {

pkg/analyzer/test/src/diagnostics/on_repeated_test.dart

@@ -2,7 +2,6 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-import 'package:analyzer/src/diagnostic/diagnostic.dart' as diag;
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 
 import '../dart/resolution/context_collection_resolution.dart';
@@ -28,22 +27,11 @@ mixin M on A, A {}
 
   @SkippedTest() // TODO(scheglov): implement augmentation
   test_2times_augmentation() async {
-    var a = newFile('$testPackageLibPath/a.dart', r'''
-part 'b.dart';
-
+    await resolveTestCodeWithDiagnostics(r'''
 class A {}
 mixin M on A {}
-''');
-
-    var b = newFile('$testPackageLibPath/b.dart', r'''
-part of 'a.dart';
-
 augment mixin M on A {}
 ''');
-
-    await assertErrorsInFile2(a, []);
-
-    await assertErrorsInFile2(b, [error(diag.onRepeated, 38, 1)]);
   }
 
   test_2times_viaTypeAlias() async {

pkg/analyzer/test/src/diagnostics/return_of_do_not_store_test.dart

@@ -43,9 +43,9 @@ class A {
   test_noHintsInTestDir() async {
     // Code that is in a test dir should not trigger the hint.
     // (See:https://github.com/dart-lang/sdk/issues/45594)
-    var result = await resolveFileCode(
-      '$testPackageRootPath/test/test.dart',
-      r'''
+    var file = getFile('$testPackageRootPath/test/test.dart');
+
+    await resolveFileWithDiagnostics(file, r'''
 import 'package:meta/meta.dart';
 
 @doNotStore
@@ -59,9 +59,7 @@ String f() {
 String g() {
   return _v;
 }
-''',
-    );
-    assertNoErrorsInTestResult(result);
+''');
   }
 
   test_returnFromClosureInFunction() async {

pkg/analyzer/test/src/diagnostics/unnecessary_import_test.dart

@@ -2,7 +2,6 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-import 'package:analyzer/src/diagnostic/diagnostic.dart' as diag;
 import 'package:test/test.dart';
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 
@@ -188,15 +187,19 @@ f(A a1, p.A a2, B b) {}
 
   @FailingTest(issue: 'https://github.com/dart-lang/sdk/issues/61877')
   test_library_export_and_export() async {
-    var a = newFile('$testPackageLibPath/a.dart', r'''
+    var a = getFile('$testPackageLibPath/a.dart');
+    var b = getFile('$testPackageLibPath/b.dart');
+    var c = getFile('$testPackageLibPath/c.dart');
+
+    await resolveFileWithDiagnostics(a, r'''
 class C {}
 ''');
 
-    var b = newFile('$testPackageLibPath/b.dart', r'''
+    await resolveFileWithDiagnostics(b, r'''
 export 'a.dart';
 ''');
 
-    var c = newFile('$testPackageLibPath/c.dart', r'''
+    await resolveFileWithDiagnostics(c, r'''
 export 'a.dart';
 ''');
 
@@ -206,9 +209,6 @@ import 'c.dart';
 
 method() => C();
 ''');
-    await assertErrorsInFile2(a, []);
-    await assertErrorsInFile2(b, []);
-    await assertErrorsInFile2(c, []);
     // Import of 'c.dart' is not marked as unused even though it could be
     // removed.
     var result = await resolveFile(d);
@@ -386,11 +386,14 @@ f(A a, B b) {}
 
   @FailingTest(issue: 'https://github.com/dart-lang/sdk/issues/61877')
   test_library_import_and_export() async {
-    var a = newFile('$testPackageLibPath/a.dart', r'''
+    var a = getFile('$testPackageLibPath/a.dart');
+    var b = getFile('$testPackageLibPath/b.dart');
+
+    await resolveFileWithDiagnostics(a, r'''
 class C {}
 ''');
 
-    var b = newFile('$testPackageLibPath/b.dart', r'''
+    await resolveFileWithDiagnostics(b, r'''
 export 'a.dart';
 ''');
 
@@ -400,8 +403,6 @@ import 'b.dart';
 
 method() => C();
 ''');
-    await assertErrorsInFile2(a, []);
-    await assertErrorsInFile2(b, []);
     // Import of 'b.dart' is not marked as unused even though it could be
     // removed.
     var result = await resolveFile(c);
@@ -492,20 +493,22 @@ class A {}
 class B {}
 ''');
 
-    var a = newFile('$testPackageLibPath/a.dart', r'''
-part 'b.dart';
-''');
+    var a = getFile('$testPackageLibPath/a.dart');
+    var b = getFile('$testPackageLibPath/b.dart');
 
-    var b = newFile('$testPackageLibPath/b.dart', r'''
+    await resolveFilesWithDiagnostics({
+      a: r'''
+part 'b.dart';
+''',
+      b: r'''
 part of 'a.dart';
 import 'x.dart' hide B;
+//     ^^^^^^^^
+// [diag.unnecessaryImport] The import of 'x.dart' is unnecessary because all of the used elements are also provided by the import of 'x.dart'.
 import 'x.dart';
 void f(A _, B _) {}
-''');
-
-    await assertErrorsInFile2(a, []);
-
-    await assertErrorsInFile2(b, [error(diag.unnecessaryImport, 25, 8)]);
+''',
+    });
   }
 
   test_part_inside_unnecessary_prefixed() async {
@@ -514,19 +517,21 @@ class A {}
 class B {}
 ''');
 
-    var a = newFile('$testPackageLibPath/a.dart', r'''
-part 'b.dart';
-''');
+    var a = getFile('$testPackageLibPath/a.dart');
+    var b = getFile('$testPackageLibPath/b.dart');
 
-    var b = newFile('$testPackageLibPath/b.dart', r'''
+    await resolveFilesWithDiagnostics({
+      a: r'''
+part 'b.dart';
+''',
+      b: r'''
 part of 'a.dart';
 import 'x.dart' as prefix hide B;
+//     ^^^^^^^^
+// [diag.unnecessaryImport] The import of 'x.dart' is unnecessary because all of the used elements are also provided by the import of 'x.dart'.
 import 'x.dart' as prefix;
 void f(prefix.A _, prefix.B _) {}
-''');
-
-    await assertErrorsInFile2(a, []);
-
-    await assertErrorsInFile2(b, [error(diag.unnecessaryImport, 25, 8)]);
+''',
+    });
   }
 }

pkg/analyzer/test/src/diagnostics/unused_import_test.dart

@@ -2,7 +2,6 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-import 'package:analyzer/src/diagnostic/diagnostic.dart' as diag;
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 
 import '../dart/resolution/context_collection_resolution.dart';
@@ -200,21 +199,22 @@ extension E on int {
 }
 ''');
 
-    var b = newFile('$testPackageLibPath/b.dart', r'''
+    var b = getFile('$testPackageLibPath/b.dart');
+    var c = getFile('$testPackageLibPath/c.dart');
+
+    await resolveFilesWithDiagnostics({
+      b: r'''
 import 'a.dart';
 part 'c.dart';
-''');
-
-    var c = newFile('$testPackageLibPath/c.dart', r'''
+''',
+      c: r'''
 part of 'b.dart';
 
 void f() {
   0.foo();
 }
-''');
-
-    await assertErrorsInFile2(b, []);
-    await assertErrorsInFile2(c, []);
+''',
+    });
   }
 
   test_library_extension_instance_operator_binary() async {
@@ -590,20 +590,21 @@ extension E on int {
 }
 ''');
 
-    var a = newFile('$testPackageLibPath/a.dart', r'''
+    var a = getFile('$testPackageLibPath/a.dart');
+    var b = getFile('$testPackageLibPath/b.dart');
+
+    await resolveFilesWithDiagnostics({
+      a: r'''
 import 'x.dart';
 part 'b.dart';
-''');
-
-    var b = newFile('$testPackageLibPath/b.dart', r'''
+''',
+      b: r'''
 part of 'a.dart';
 void f() {
   0.foo();
 }
-''');
-
-    await assertErrorsInFile2(a, []);
-    await assertErrorsInFile2(b, []);
+''',
+    });
   }
 
   test_part_extension_usedPartImport() async {
@@ -613,20 +614,21 @@ extension E on int {
 }
 ''');
 
-    var a = newFile('$testPackageLibPath/a.dart', r'''
-part 'b.dart';
-''');
+    var a = getFile('$testPackageLibPath/a.dart');
+    var b = getFile('$testPackageLibPath/b.dart');
 
-    var b = newFile('$testPackageLibPath/b.dart', r'''
+    await resolveFilesWithDiagnostics({
+      a: r'''
+part 'b.dart';
+''',
+      b: r'''
 part of 'a.dart';
 import 'x.dart';
 void f() {
   0.foo();
 }
-''');
-
-    await assertErrorsInFile2(a, []);
-    await assertErrorsInFile2(b, []);
+''',
+    });
   }
 
   test_part_extension_usedPartImport_inNestedPart() async {
@@ -636,124 +638,131 @@ extension E on int {
 }
 ''');
 
-    var a = newFile('$testPackageLibPath/a.dart', r'''
-part 'b.dart';
-''');
+    var a = getFile('$testPackageLibPath/a.dart');
+    var b = getFile('$testPackageLibPath/b.dart');
+    var c = getFile('$testPackageLibPath/c.dart');
 
-    var b = newFile('$testPackageLibPath/b.dart', r'''
+    await resolveFilesWithDiagnostics({
+      a: r'''
+part 'b.dart';
+''',
+      b: r'''
 part of 'a.dart';
 import 'x.dart';
 part 'c.dart';
-''');
-
-    var c = newFile('$testPackageLibPath/c.dart', r'''
+''',
+      c: r'''
 part of 'b.dart';
 void f() {
   0.foo();
 }
-''');
-
-    await assertErrorsInFile2(a, []);
-    await assertErrorsInFile2(b, []);
-    await assertErrorsInFile2(c, []);
+''',
+    });
   }
 
   test_part_notUsedPartImport() async {
-    var a = newFile('$testPackageLibPath/a.dart', r'''
-part 'b.dart';
-''');
+    var a = getFile('$testPackageLibPath/a.dart');
+    var b = getFile('$testPackageLibPath/b.dart');
 
-    var b = newFile('$testPackageLibPath/b.dart', r'''
+    await resolveFilesWithDiagnostics({
+      a: r'''
+part 'b.dart';
+''',
+      b: r'''
 part of 'a.dart';
 import 'dart:math';
-''');
-
-    await assertErrorsInFile2(a, []);
-
-    await assertErrorsInFile2(b, [error(diag.unusedImport, 25, 11)]);
+//     ^^^^^^^^^^^
+// [diag.unusedImport] Unused import: 'dart:math'.
+''',
+    });
   }
 
   test_part_usedLibraryImport() async {
-    var a = newFile('$testPackageLibPath/a.dart', r'''
+    var a = getFile('$testPackageLibPath/a.dart');
+    var b = getFile('$testPackageLibPath/b.dart');
+
+    await resolveFilesWithDiagnostics({
+      a: r'''
 import 'dart:math';
 part 'b.dart';
-''');
-
-    var b = newFile('$testPackageLibPath/b.dart', r'''
+''',
+      b: r'''
 part of 'a.dart';
 void f(Random _) {}
-''');
-
-    await assertErrorsInFile2(a, []);
-    await assertErrorsInFile2(b, []);
+''',
+    });
   }
 
   test_part_usedLibraryImport_usedPartImport() async {
-    var a = newFile('$testPackageLibPath/a.dart', r'''
+    var a = getFile('$testPackageLibPath/a.dart');
+    var b = getFile('$testPackageLibPath/b.dart');
+
+    await resolveFilesWithDiagnostics({
+      a: r'''
 import 'dart:math';
 part 'b.dart';
-''');
-
-    var b = newFile('$testPackageLibPath/b.dart', r'''
+''',
+      b: r'''
 part of 'a.dart';
 import 'dart:async';
 void f(Random _, Future<int> _) {}
-''');
-
-    await assertErrorsInFile2(a, []);
-    await assertErrorsInFile2(b, []);
+''',
+    });
   }
 
   test_part_usedPartImport() async {
-    var a = newFile('$testPackageLibPath/a.dart', r'''
-part 'b.dart';
-''');
+    var a = getFile('$testPackageLibPath/a.dart');
+    var b = getFile('$testPackageLibPath/b.dart');
 
-    var b = newFile('$testPackageLibPath/b.dart', r'''
+    await resolveFilesWithDiagnostics({
+      a: r'''
+part 'b.dart';
+''',
+      b: r'''
 part of 'a.dart';
 import 'dart:math';
 void f(Random _) {}
-''');
-
-    await assertErrorsInFile2(a, []);
-    await assertErrorsInFile2(b, []);
+''',
+    });
   }
 
   test_part_usedPartImport_inNestedPart() async {
-    var a = newFile('$testPackageLibPath/a.dart', r'''
-part 'b.dart';
-''');
+    var a = getFile('$testPackageLibPath/a.dart');
+    var b = getFile('$testPackageLibPath/b.dart');
+    var c = getFile('$testPackageLibPath/c.dart');
 
-    var b = newFile('$testPackageLibPath/b.dart', r'''
+    await resolveFilesWithDiagnostics({
+      a: r'''
+part 'b.dart';
+''',
+      b: r'''
 part of 'a.dart';
 import 'dart:math';
 part 'c.dart';
-''');
-
-    var c = newFile('$testPackageLibPath/c.dart', r'''
+''',
+      c: r'''
 part of 'b.dart';
 void f(Random _) {}
-''');
-
-    await assertErrorsInFile2(a, []);
-    await assertErrorsInFile2(b, []);
-    await assertErrorsInFile2(c, []);
+''',
+    });
   }
 
   test_part_usedPartImport_notUsedLibraryImport() async {
-    var a = newFile('$testPackageLibPath/a.dart', r'''
-import 'dart:math';
-part 'b.dart';
-''');
+    var a = getFile('$testPackageLibPath/a.dart');
+    var b = getFile('$testPackageLibPath/b.dart');
 
-    var b = newFile('$testPackageLibPath/b.dart', r'''
+    await resolveFilesWithDiagnostics({
+      a: r'''
+import 'dart:math';
+//     ^^^^^^^^^^^
+// [diag.unusedImport] Unused import: 'dart:math'.
+part 'b.dart';
+''',
+      b: r'''
 part of 'a.dart';
 import 'dart:math';
 void f(Random _) {}
-''');
-
-    await assertErrorsInFile2(a, [error(diag.unusedImport, 7, 11)]);
-
-    await assertErrorsInFile2(b, []);
+''',
+    });
   }
 }

pkg/analyzer/test/src/ignore_comments/diagnostic_suppression_test.dart

@@ -2,7 +2,6 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-import 'package:analyzer/src/diagnostic/diagnostic.dart' as diag;
 import 'package:analyzer_testing/utilities/utilities.dart';
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 
@@ -273,27 +272,31 @@ int y = (0 as int);
   }
 
   test_undefinedFunctionWithinFlutterCanBeIgnored() async {
-    await assertErrorsInFile('$workspaceRootPath/flutterlib/flutter.dart', '''
+    var file = getFile('$workspaceRootPath/flutter/lib/flutter.dart');
+
+    await resolveFileWithDiagnostics(file, '''
 // ignore: undefined_function
 f() => g();
-''', []);
+''');
   }
 
   test_undefinedFunctionWithinFlutterWithoutIgnore() async {
-    await assertErrorsInFile(
-      '$workspaceRootPath/flutterlib/flutter.dart',
-      '''
+    var file = getFile('$workspaceRootPath/flutter/lib/flutter.dart');
+
+    await resolveFileWithDiagnostics(file, '''
 f() => g();
-''',
-      [error(diag.undefinedFunction, 7, 1)],
-    );
+//     ^
+// [diag.undefinedFunction] The function 'g' isn't defined.
+''');
   }
 
   test_undefinedPrefixedNameWithinFlutterCanBeIgnored() async {
-    await assertErrorsInFile('$workspaceRootPath/flutterlib/flutter.dart', '''
+    var file = getFile('$workspaceRootPath/flutter/lib/flutter.dart');
+
+    await resolveFileWithDiagnostics(file, '''
 import 'dart:collection' as c;
 // ignore: undefined_prefixed_name
 f() => c.g;
-''', []);
+''');
   }
 }

pkg/analyzer_testing/lib/src/expected_diagnostics.dart

@@ -3,6 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 import 'package:analyzer/diagnostic/diagnostic.dart';
+import 'package:analyzer/file_system/file_system.dart';
 import 'package:analyzer/source/line_info.dart';
 import 'package:analyzer_testing/utilities/extensions/diagnostic_code.dart';
 
@@ -51,6 +52,88 @@ String updateExpectedDiagnostics({
   return _ExpectedDiagnosticsUpdater(content).update(actualDiagnostics);
 }
 
+/// Returns each file's content with canonical diagnostic expectation markers.
+///
+/// This is the multi-file form of [updateExpectedDiagnostics]. It supports
+/// diagnostics whose context messages are located in another file in
+/// [contentByFile].
+Map<File, String> updateExpectedDiagnosticsForFiles({
+  required Map<File, String> contentByFile,
+  required Map<File, List<Diagnostic>> actualDiagnosticsByFile,
+}) {
+  return _ExpectedDiagnosticsForFilesUpdater(
+    contentByFile,
+  ).update(actualDiagnosticsByFile);
+}
+
+final class _ExpectedDiagnosticsForFilesUpdater {
+  final Map<File, _ExpectedDiagnosticsUpdater> updatersByFile = {};
+  final Map<String, _ExpectedDiagnosticsUpdater> updatersByPath = {};
+
+  int nextMarkerIndex = 0;
+  int nextContextId = 1;
+
+  _ExpectedDiagnosticsForFilesUpdater(Map<File, String> contentByFile) {
+    for (var entry in contentByFile.entries) {
+      var updater = _ExpectedDiagnosticsUpdater(entry.value);
+      updatersByFile[entry.key] = updater;
+      updatersByPath[entry.key.path] = updater;
+    }
+  }
+
+  Map<File, String> update(
+    Map<File, List<Diagnostic>> actualDiagnosticsByFile,
+  ) {
+    for (var entry in actualDiagnosticsByFile.entries) {
+      var updater = _updaterForPath(entry.key.path);
+      var sortedDiagnostics = entry.value.toList()
+        ..sort((first, second) => first.offset.compareTo(second.offset));
+      for (var diagnostic in sortedDiagnostics) {
+        _generateDiagnosticMarkers(updater, diagnostic);
+      }
+    }
+
+    return {
+      for (var entry in updatersByFile.entries)
+        entry.key: entry.value._writeContent(),
+    };
+  }
+
+  void _generateDiagnosticMarkers(
+    _ExpectedDiagnosticsUpdater diagnosticUpdater,
+    Diagnostic diagnostic,
+  ) {
+    var contextRefs = <int>[];
+    for (var contextMessage in diagnostic.contextMessages) {
+      var contextUpdater = _updaterForPath(contextMessage.filePath);
+      var id = nextContextId++;
+      contextRefs.add(id);
+      contextUpdater._addContextMessageMarker(
+        contextMessage,
+        id: id,
+        index: nextMarkerIndex++,
+      );
+    }
+
+    diagnosticUpdater._addDiagnosticMarker(
+      diagnostic,
+      index: nextMarkerIndex++,
+      contextRefs: contextRefs,
+    );
+  }
+
+  _ExpectedDiagnosticsUpdater _updaterForPath(String path) {
+    var updater = updatersByPath[path];
+    if (updater == null) {
+      throw StateError(
+        'Cannot generate diagnostic expectations for $path: '
+        'no content was provided.',
+      );
+    }
+    return updater;
+  }
+}
+
 final class _ExpectedDiagnosticsUpdater {
   final List<_Line> lines;
   final LineInfo lineInfo;
@@ -77,6 +160,61 @@ final class _ExpectedDiagnosticsUpdater {
     return _writeContent();
   }
 
+  void _addContextMessageMarker(
+    DiagnosticMessage contextMessage, {
+    required int id,
+    required int index,
+  }) {
+    var location = _markerLocation(offset: contextMessage.offset);
+    var line = lines[location.lineNumber - 1];
+    var presentation = _markerPresentation(
+      line,
+      column: location.column,
+      length: contextMessage.length,
+    );
+    _addMarker(
+      location.lineNumber,
+      _GeneratedMarker.context(
+        offset: contextMessage.offset,
+        index: index,
+        id: id,
+        column: location.column,
+        length: contextMessage.length,
+        caretLength: presentation.caretLength,
+        includeExplicitLocation: presentation.includeExplicitLocation,
+        message: _messageText(contextMessage),
+      ),
+    );
+  }
+
+  void _addDiagnosticMarker(
+    Diagnostic diagnostic, {
+    required int index,
+    required List<int> contextRefs,
+  }) {
+    var location = _markerLocation(offset: diagnostic.offset);
+    var line = lines[location.lineNumber - 1];
+    var presentation = _markerPresentation(
+      line,
+      column: location.column,
+      length: diagnostic.length,
+    );
+    _addMarker(
+      location.lineNumber,
+      _GeneratedMarker.diagnostic(
+        offset: diagnostic.offset,
+        index: index,
+        constantName: diagnostic.diagnosticCode.constantName,
+        column: location.column,
+        length: diagnostic.length,
+        caretLength: presentation.caretLength,
+        includeExplicitLocation: presentation.includeExplicitLocation,
+        contextRefs: contextRefs,
+        message: _messageText(diagnostic.problemMessage),
+      ),
+    );
+  }
+
   void _addMarker(int lineNumber, _GeneratedMarker marker) {
     markersByLine.putIfAbsent(lineNumber, () => []).add(marker);
   }
@@ -90,58 +228,25 @@ final class _ExpectedDiagnosticsUpdater {
     var contextRefs = <int>[];
     for (var contextMessage in diagnostic.contextMessages) {
       if (contextMessage.filePath != diagnostic.problemMessage.filePath) {
-        // TODO(scheglov): Support generating expectations for context
-        // messages in other files.
         throw StateError(
           'Cannot generate a diagnostic expectation with a context message '
-          'in another file.',
+          'in another file. Use updateExpectedDiagnosticsForFiles instead.',
         );
       }
 
       var id = nextContextId++;
       contextRefs.add(id);
-      var location = _markerLocation(offset: contextMessage.offset);
-      var line = lines[location.lineNumber - 1];
-      var presentation = _markerPresentation(
-        line,
-        column: location.column,
-        length: contextMessage.length,
-      );
-      _addMarker(
-        location.lineNumber,
-        _GeneratedMarker.context(
-          offset: contextMessage.offset,
-          index: nextMarkerIndex++,
-          id: id,
-          column: location.column,
-          length: contextMessage.length,
-          caretLength: presentation.caretLength,
-          includeExplicitLocation: presentation.includeExplicitLocation,
-          message: _messageText(contextMessage),
-        ),
+      _addContextMessageMarker(
+        contextMessage,
+        id: id,
+        index: nextMarkerIndex++,
       );
     }
 
-    var location = _markerLocation(offset: diagnostic.offset);
-    var line = lines[location.lineNumber - 1];
-    var presentation = _markerPresentation(
-      line,
-      column: location.column,
-      length: diagnostic.length,
-    );
-    _addMarker(
-      location.lineNumber,
-      _GeneratedMarker.diagnostic(
-        offset: diagnostic.offset,
-        index: nextMarkerIndex++,
-        constantName: diagnostic.diagnosticCode.constantName,
-        column: location.column,
-        length: diagnostic.length,
-        caretLength: presentation.caretLength,
-        includeExplicitLocation: presentation.includeExplicitLocation,
-        contextRefs: contextRefs,
-        message: _messageText(diagnostic.problemMessage),
-      ),
+    _addDiagnosticMarker(
+      diagnostic,
+      index: nextMarkerIndex++,
+      contextRefs: contextRefs,
     );
   }