analyzer_testing: Deprecate the flutter_test mock; only used in two DAS tests.

Work towards https://github.com/dart-lang/sdk/issues/61597

Change-Id: I32caa38bff42ad9117829cca9be8b892da228a9e
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/472960
Commit-Queue: Samuel Rawlins <srawlins@google.com>
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>

pkg/analysis_server/test/support/configuration_files.dart

@@ -78,8 +78,24 @@ mixin ConfigurationFilesMixin on MockPackagesMixin {
     }
 
     if (addFlutterTestPackageDep) {
-      var libFolder = addFlutterTest();
-      config.add(name: 'flutter_test', rootPath: libFolder.parent.path);
+      var flutterTestRootPath = '/packages/flutter_test';
+
+      var flutterTestRoot = resourceProvider.getFolder(flutterTestRootPath);
+      var libFolder = flutterTestRoot.getChildAssumingFolder('lib')..create();
+      libFolder.getChildAssumingFile('flutter_test.dart').writeAsStringSync(r'''
+void test(Object description, dynamic Function() body) {}
+
+void group(Object description, void Function() body) {}
+
+void main() {
+  // Because this file is called 'flutter_test.dart' and is inside the 'test'
+  // folder, it will be considered a test suite. To avoid it failing the bots
+  // with "Invoked Dart programs must have a 'main' function defined", provide
+  // an empty main function.
+}
+
+''');
+      config.add(name: 'flutter_test', rootPath: flutterTestRootPath);
     }
 
     if (addVectorMathPackageDep) {

pkg/analyzer_testing/CHANGELOG.md

@@ -1,5 +1,7 @@
 ## 0.1.9-dev
 - Deprecate `MockPackagesMixin.addUI`; This is replaced by `addSkyEngine`.
+- Deprecate `MockPackagesMixin.addFlutterTest`. A mock `flutter_test` package
+  can still be written with `PubPackageResolutionTest.newPackage`.
 
 ## 0.1.8
 

pkg/analyzer_testing/api.txt

@@ -29,7 +29,7 @@ package:analyzer_testing/mock_packages/mock_packages.dart:
     addFfi (method: Folder Function())
     addFixnum (method: Folder Function())
     addFlutter (method: Folder Function())
-    addFlutterTest (method: Folder Function())
+    addFlutterTest (method: Folder Function(), deprecated)
     addJs (method: Folder Function(), deprecated)
     addKernel (method: Folder Function(), deprecated)
     addMeta (method: Folder Function())

pkg/analyzer_testing/lib/mock_packages/mock_packages.dart

@@ -141,6 +141,10 @@ mixin MockPackagesMixin {
     return packageFolder.getChildAssumingFolder('lib');
   }
 
+  @Deprecated(
+    'The mock flutter_test package is deprecated; use '
+    '`PubPackageResolutionTest.newPackage` to make a custom mock',
+  )
   Folder addFlutterTest() {
     var packageFolder = _addFiles('flutter_test');
     return packageFolder.getChildAssumingFolder('lib');