diff --git a/tests/language/constructor/missing_initializer_test.dart b/tests/language/constructor/missing_initializer_test.dart
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+// Copyright (c) 2020, the Dart project authors.  Please see the AUTHORS file
+// 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.
+
+// Test that it is an error for a class with no generative constructors to
+// have a final instance variable without an initializing expression, except
+// if it is `abstract` or `external`. The latter also holds in a class with
+// generative constructors.
+
+// Has factory, hence no default, hence no generative constructors.
+abstract class A {
+  final dynamic n;
+  //            ^
+  // [analyzer] COMPILE_TIME_ERROR.FINAL_NOT_INITIALIZED
+  // [cfe] unspecified
+
+  // Uninitialized, but no errors.
+  abstract final int x1;
+  abstract final int? x2;
+  external final String x3;
+  external final String? x4;
+
+  factory A() = B;
+}
+
+class B implements A {
+  dynamic get n => 1;
+  int get x1 => 1;
+  int? get x2 => null;
+  String get x3 => "";
+  String? get x4 => null;
+}
+
+class C = Object with A;
+
+// Has a generative constructor: default.
+abstract class D {
+  // Uninitialized, but no errors.
+  abstract final int x1;
+  abstract final int? x2;
+  external final String x3;
+  external final String? x4;
+}
+
+void main() {
+  A();
+  C();
+  var _ = D;
+}