Move leading_newlines_in_multiline_strings tests (#4689)

test/rules/all.dart

@@ -67,6 +67,8 @@ import 'hash_and_equals_test.dart' as hash_and_equals;
 import 'implicit_reopen_test.dart' as implicit_reopen;
 import 'invalid_case_patterns_test.dart' as invalid_case_patterns;
 import 'join_return_with_assignment_test.dart' as join_return_with_assignment;
+import 'leading_newlines_in_multiline_strings_test.dart'
+    as leading_newlines_in_multiline_strings;
 import 'library_annotations_test.dart' as library_annotations;
 import 'library_names_test.dart' as library_names;
 import 'library_private_types_in_public_api_test.dart'
@@ -265,6 +267,7 @@ void main() {
   implicit_reopen.main();
   invalid_case_patterns.main();
   join_return_with_assignment.main();
+  leading_newlines_in_multiline_strings.main();
   library_annotations.main();
   library_names.main();
   library_private_types_in_public_api.main();

test/rules/leading_newlines_in_multiline_strings_test.dart

@@ -0,0 +1,85 @@
+// 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(LeadingNewlinesInMultilineStringsTest);
+  });
+}
+
+@reflectiveTest
+class LeadingNewlinesInMultilineStringsTest extends LintRuleTest {
+  @override
+  String get lintRule => 'leading_newlines_in_multiline_strings';
+
+  test_emptyString() async {
+    await assertNoDiagnostics(r"""
+var x = '''''';
+""");
+  }
+
+  test_leadingNewline() async {
+    await assertNoDiagnostics(r"""
+var x = '''
+this is a multiline string''';
+""");
+  }
+
+  test_leadingNewline_withInterpolation() async {
+    await assertNoDiagnostics(r"""
+var a = 'a';
+var x = '''
+this is a multiline string $a''';
+""");
+  }
+
+  test_noNewline() async {
+    await assertNoDiagnostics(r"""
+var x = '''this is a multiline string''';
+""");
+  }
+
+  test_noNewline_doubleQuotes() async {
+    await assertNoDiagnostics(r'''
+var x = """uses double quotes""";
+''');
+  }
+
+  test_noNewline_interpolation() async {
+    await assertNoDiagnostics(r"""
+var a = 'a';
+var x = '''$a''';
+""");
+  }
+
+  test_noNewline_withInterpolation() async {
+    await assertNoDiagnostics(r"""
+var a = 'a';
+var x = '''this is a multiline string $a''';
+""");
+  }
+
+  test_textBeforeNewline() async {
+    await assertDiagnostics(r"""
+var x = '''this
+ is a multiline string''';
+""", [
+      lint(8, 33),
+    ]);
+  }
+
+  test_textBeforeNewline_withInterpolation() async {
+    await assertDiagnostics(r"""
+var a = 'a';
+var x = '''this
+ is a multiline string$a''';
+""", [
+      lint(21, 35),
+    ]);
+  }
+}