flutter-add-widget-test

Use the testWidgets function with a WidgetTester callback, call tester.pumpWidget to render your widget, then use Finder objects with expect and Matchers like findsOneWidget to verify the UI. Wrap widgets in MaterialApp when they need theme or directionality context.

pump triggers a single frame rebuild, which suits simple state changes like button taps. pumpAndSettle repeatedly pumps frames until no more are scheduled, making it necessary for animations, transitions, and asynchronous UI updates.

Use tester.scrollUntilVisible with the target item finder, a scroll delta, and the scrollable finder to bring off-screen items into view before interacting with them. This ensures dynamically built list items are rendered before assertions.

Common causes include missing pump calls after state changes, widgets not yet built in lazy lists, or absent MaterialApp or Directionality ancestors. Verify the Finder matches the widget tree and pump frames after each interaction.

Place all test files in the test directory at the project root and suffix file names with _test.dart. Add flutter_test to the dev_dependencies section of pubspec.yaml before running flutter test.