linter: Move avoid_multiple_declarations_per_line tests

Change-Id: I92271ad7999c521ea343c3199dc09f32a897b0c7
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/329140
Auto-Submit: Samuel Rawlins <[email protected]>
Reviewed-by: Phil Quitslund <[email protected]>
Commit-Queue: Phil Quitslund <[email protected]>

Author: srawlins

pkg/linter/test/rules/all.dart

@@ -16,6 +16,8 @@ import 'avoid_final_parameters_test.dart' as avoid_final_parameters;
 import 'avoid_function_literals_in_foreach_calls_test.dart'
     as avoid_function_literals_in_foreach_calls;
 import 'avoid_init_to_null_test.dart' as avoid_init_to_null;
+import 'avoid_multiple_declarations_per_line_test.dart'
+    as avoid_multiple_declarations_per_line;
 import 'avoid_positional_boolean_parameters_test.dart'
     as avoid_positional_boolean_parameters;
 import 'avoid_print_test.dart' as avoid_print;
@@ -260,6 +262,7 @@ void main() {
   avoid_final_parameters.main();
   avoid_function_literals_in_foreach_calls.main();
   avoid_init_to_null.main();
+  avoid_multiple_declarations_per_line.main();
   avoid_positional_boolean_parameters.main();
   avoid_print.main();
   avoid_private_typedef_functions.main();

pkg/linter/test/rules/avoid_multiple_declarations_per_line_test.dart

@@ -0,0 +1,96 @@
+// 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(() {
+    defineReflectiveTests(AvoidMultipleDeclarationsPerLineTest);
+  });
+}
+
+@reflectiveTest
+class AvoidMultipleDeclarationsPerLineTest extends LintRuleTest {
+  @override
+  String get lintRule => 'avoid_multiple_declarations_per_line';
+
+  test_extensionField_multiple() async {
+    await assertDiagnostics(r'''
+extension E on Object {
+  static String? a, b, c;
+}
+''', [
+      lint(44, 1),
+    ]);
+  }
+
+  test_extensionField_single() async {
+    await assertNoDiagnostics(r'''
+extension E on Object {
+  static String? a;
+}
+''');
+  }
+
+  test_field_multiple() async {
+    await assertDiagnostics(r'''
+class C {
+  String? a, b, c;
+}
+''', [
+      lint(23, 1),
+    ]);
+  }
+
+  test_field_single() async {
+    await assertNoDiagnostics(r'''
+class C {
+  String? a;
+}
+''');
+  }
+
+  test_forLoop_multiple() async {
+    await assertNoDiagnostics(r'''
+// See https://github.com/dart-lang/linter/issues/2543.
+void f() {
+  for (var i = 0, j = 0; i < 2 && j < 2; ++i, ++j) {}
+}
+''');
+  }
+
+  test_functionVariable_multiple() async {
+    await assertDiagnostics(r'''
+void f() {
+  String? a, b, c;
+}
+''', [
+      lint(24, 1),
+    ]);
+  }
+
+  test_functionVariable_single() async {
+    await assertNoDiagnostics(r'''
+void f() {
+  String? a;
+}
+''');
+  }
+
+  test_topLevel_multiple() async {
+    await assertDiagnostics(r'''
+String? a, b, c;
+''', [
+      lint(11, 1),
+    ]);
+  }
+
+  test_topLevel_single() async {
+    await assertNoDiagnostics(r'''
+String? a;
+''');
+  }
+}