Widen getText support for RichText with multiple text spans in driver (#75603)

packages/flutter_driver/lib/src/common/handler_factory.dart

@@ -390,9 +390,10 @@ mixin CommandHandlerFactory {
       text = (widget as Text).data;
     } else if (widget.runtimeType == RichText) {
       final RichText richText = widget as RichText;
-      if (richText.text.runtimeType == TextSpan) {
-        text = (richText.text as TextSpan).text;
-      }
+      text = richText.text.toPlainText(
+        includeSemanticsLabels: false,
+        includePlaceholders: false,
+      );
     } else if (widget.runtimeType == TextField) {
       text = (widget as TextField).controller?.text;
     } else if (widget.runtimeType == TextFormField) {

packages/flutter_driver/test/src/real_tests/extension_test.dart

@@ -599,6 +599,18 @@ void main() {
                       controller: TextEditingController(text: 'Hello5'),
                     ),
                   ),
+                  Container(
+                    height: 25.0,
+                    child: RichText(
+                      key: const ValueKey<String>('text6'),
+                      text: const TextSpan(children: <TextSpan>[
+                        TextSpan(text: 'Hello'),
+                        TextSpan(text: ', '),
+                        TextSpan(text: 'World'),
+                        TextSpan(text: '!'),
+                      ]),
+                    ),
+                  ),
                 ],
               ))
           )
@@ -609,6 +621,7 @@ void main() {
       expect(await getTextInternal(ByValueKey('text3')), 'Hello3');
       expect(await getTextInternal(ByValueKey('text4')), 'Hello4');
       expect(await getTextInternal(ByValueKey('text5')), 'Hello5');
+      expect(await getTextInternal(ByValueKey('text6')), 'Hello, World!');
 
       // Check if error thrown for other types
       final Map<String, String> arguments = GetText(ByValueKey('column'), timeout: const Duration(seconds: 1)).serialize();