Move use_setters_to_change_properties tests

test/rules/all.dart

@@ -174,6 +174,8 @@ import 'use_key_in_widget_constructors_test.dart'
 import 'use_late_for_private_fields_and_variables_test.dart'
     as use_late_for_private_fields_and_variables;
 import 'use_named_constants_test.dart' as use_named_constants;
+import 'use_setters_to_change_properties_test.dart'
+    as use_setters_to_change_properties;
 import 'use_super_parameters_test.dart' as use_super_parameters;
 import 'use_test_throws_matchers_test.dart' as use_test_throws_matchers;
 import 'void_checks_test.dart' as void_checks;
@@ -305,6 +307,7 @@ void main() {
   use_key_in_widget_constructors.main();
   use_late_for_private_fields_and_variables.main();
   use_named_constants.main();
+  use_setters_to_change_properties.main();
   use_super_parameters.main();
   use_test_throws_matchers.main();
   void_checks.main();

test/rules/use_setters_to_change_properties_test.dart

@@ -0,0 +1,110 @@
+// Copyright (c) 2023, 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.
+
+import 'package:test_reflective_loader/test_reflective_loader.dart';
+
+import '../rule_test_support.dart';
+
+main() {
+  defineReflectiveSuite(() {
+    // TODO(srawlins): Add test with setter-like with multiple statements; add
+    // test with non-trivial right side (`this.x = x + 1`).
+    defineReflectiveTests(UseSettersToChangePropertiesTest);
+  });
+}
+
+@reflectiveTest
+class UseSettersToChangePropertiesTest extends LintRuleTest {
+  @override
+  String get lintRule => 'use_setters_to_change_properties';
+
+  test_setterLike_expressionBody() async {
+    await assertDiagnostics(r'''
+abstract class A {
+  int x = 0;
+  void setX(int x) => this.x = x;
+}
+''', [
+      lint(39, 4),
+    ]);
+  }
+
+  test_setterLike_blockBody() async {
+    await assertDiagnostics(r'''
+abstract class A {
+  int x = 0;
+  void setX(int x) {
+    this.x = x;
+  }
+}
+''', [
+      lint(39, 4),
+    ]);
+  }
+
+  test_combo() async {
+    await assertNoDiagnostics(r'''
+abstract class A {
+  int x = 0;
+  void setX(int x) => this.x += x;
+}
+''');
+  }
+
+  test_inheritedFromSuperclass() async {
+    await assertNoDiagnostics(r'''
+abstract class A {
+  void setX(int x);
+}
+
+class B extends A {
+  int x = 0;
+
+  void setX(int x) {
+    this.x = x;
+  }
+}
+''');
+  }
+
+  test_abstract() async {
+    await assertNoDiagnostics(r'''
+abstract class A {
+  void setX(int x);
+}
+''');
+  }
+
+  test_inheritedFromSuperInterface() async {
+    await assertNoDiagnostics(r'''
+abstract class A {
+  void setX(int x);
+}
+
+class B implements A {
+  int x = 0;
+
+  void setX(int x) {
+    this.x = x;
+  }
+}
+''');
+  }
+
+  test_extension() async {
+    await assertDiagnostics(r'''
+class A {
+  int x = 0;
+}
+
+extension E on A {
+  void setX(int x) {
+    this.x = x;
+  }
+}
+''', [
+      lint(52, 4),
+    ]);
+  }
+}