Find text containing in tests (#65072)

packages/flutter_test/lib/src/finders.dart

@@ -36,6 +36,20 @@ class CommonFinders {
   /// nodes that are [Offstage] or that are from inactive [Route]s.
   Finder text(String text, { bool skipOffstage = true }) => _TextFinder(text, skipOffstage: skipOffstage);
 
+  /// Finds [Text] and [EditableText] widgets which contain the given
+  /// `pattern` argument.
+  ///
+  /// ## Sample code
+  ///
+  /// ```dart
+  /// expect(find.textContain('Back'), findsOneWidget);
+  /// expect(find.textContain(RegExp(r'(\w+)')), findsOneWidget);
+  /// ```
+  ///
+  /// If the `skipOffstage` argument is true (the default), then this skips
+  /// nodes that are [Offstage] or that are from inactive [Route]s.
+  Finder textContaining(Pattern pattern, { bool skipOffstage = true }) => _TextContainingFinder(pattern, skipOffstage: skipOffstage);
+
   /// Looks for widgets that contain a [Text] descendant with `text`
   /// in it.
   ///
@@ -556,6 +570,29 @@ class _TextFinder extends MatchFinder {
   }
 }
 
+class _TextContainingFinder extends MatchFinder {
+  _TextContainingFinder(this.pattern, {bool skipOffstage = true})
+      : super(skipOffstage: skipOffstage);
+
+  final Pattern pattern;
+
+  @override
+  String get description => 'text containing $pattern';
+
+  @override
+  bool matches(Element candidate) {
+    final Widget widget = candidate.widget;
+    if (widget is Text) {
+      if (widget.data != null)
+        return widget.data.contains(pattern);
+      return widget.textSpan.toPlainText().contains(pattern);
+    } else if (widget is EditableText) {
+      return widget.controller.text.contains(pattern);
+    }
+    return false;
+  }
+}
+
 class _KeyFinder extends MatchFinder {
   _KeyFinder(this.key, { bool skipOffstage = true }) : super(skipOffstage: skipOffstage);
 

packages/flutter_test/test/finders_test.dart

@@ -30,6 +30,46 @@ void main() {
     });
   });
 
+  group('textContaining', () {
+    testWidgets('finds Text widgets', (WidgetTester tester) async {
+      await tester.pumpWidget(_boilerplate(
+        const Text('this is a test'),
+      ));
+      expect(find.textContaining(RegExp(r'test')), findsOneWidget);
+      expect(find.textContaining('test'), findsOneWidget);
+      expect(find.textContaining('a'), findsOneWidget);
+      expect(find.textContaining('s'), findsOneWidget);
+    });
+
+    testWidgets('finds Text.rich widgets', (WidgetTester tester) async {
+      await tester.pumpWidget(_boilerplate(
+          const Text.rich(
+            TextSpan(text: 'this', children: <TextSpan>[
+              TextSpan(text: 'is'),
+              TextSpan(text: 'a'),
+              TextSpan(text: 'test'),
+            ],
+            ),
+          )));
+
+      expect(find.textContaining(RegExp(r'isatest')), findsOneWidget);
+      expect(find.textContaining('isatest'), findsOneWidget);
+    });
+
+    testWidgets('finds EditableText widgets', (WidgetTester tester) async {
+      await tester.pumpWidget(MaterialApp(
+        home: Scaffold(
+          body: _boilerplate(TextField(
+            controller: TextEditingController()..text = 'this is test',
+          )),
+        ),
+      ));
+
+      expect(find.textContaining(RegExp(r'test')), findsOneWidget);
+      expect(find.textContaining('test'), findsOneWidget);
+    });
+  });
+
   group('semantics', () {
     testWidgets('Throws StateError if semantics are not enabled', (WidgetTester tester) async {
       expect(() => find.bySemanticsLabel('Add'), throwsStateError);