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In this example, you’ve learned how to use Mockito to test functions or classes
that depend on web services or databases. This is only a short introduction to
the Mockito library and the concept of mocking. For more information,
see the documentation provided by the Mockito package.
<topic_end>
<topic_start>An introduction to widget testing
In the introduction to unit testing recipe,
you learned how to test Dart classes using the test package.
To test widget classes, you need a few additional tools provided by the
flutter_test package, which ships with the Flutter SDK.The flutter_test package provides the following tools for
testing widgets:If this sounds overwhelming, don’t worry. Learn how all of these pieces fit
together throughout this recipe, which uses the following steps:<topic_end>
<topic_start>
1. Add the flutter_test dependency
Before writing tests, include the flutter_test
dependency in the dev_dependencies section of the pubspec.yaml file.
If creating a new Flutter project with the command line tools or
a code editor, this dependency should already be in place.<topic_end>
<topic_start>
2. Create a widget to test
Next, create a widget for testing. For this recipe,
create a widget that displays a title and message.
<code_start>class MyWidget extends StatelessWidget {
const MyWidget({
super.key,
required this.title,
required this.message,
});
final String title;
final String message;
@override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
home: Scaffold(
appBar: AppBar(
title: Text(title),
),
body: Center(
child: Text(message),
),
),
);
}
}<code_end>
<topic_end>
<topic_start>
3. Create a testWidgets test
With a widget to test, begin by writing your first test.
Use the testWidgets() function provided by the
flutter_test package to define a test.
The testWidgets function allows you to define a
widget test and creates a WidgetTester to work with.This test verifies that MyWidget displays a given title and message.
It is titled accordingly, and it will be populated in the next section.
<code_start>void main() {
// Define a test. The TestWidgets function also provides a WidgetTester
// to work with. The WidgetTester allows you to build and interact
// with widgets in the test environment.
testWidgets('MyWidget has a title and message', (tester) async {
// Test code goes here.
});
}<code_end>
<topic_end>
<topic_start>
4. Build the widget using the WidgetTester
Next, build MyWidget inside the test environment by using the
pumpWidget() method provided by WidgetTester.
The pumpWidget method builds and renders the provided widget.Create a MyWidget instance that displays “T” as the title
and “M” as the message.
<code_start>void main() {
testWidgets('MyWidget has a title and message', (tester) async {
// Create the widget by telling the tester to build it.
await tester.pumpWidget(const MyWidget(title: 'T', message: 'M'));
});
}<code_end>
<topic_end>
<topic_start>Notes about the pump() methods
After the initial call to pumpWidget(), the WidgetTester provides
additional ways to rebuild the same widget. This is useful if you’re
working with a StatefulWidget or animations.For example, tapping a button calls setState(), but Flutter won’t
automatically rebuild your widget in the test environment.
Use one of the following methods to ask Flutter to rebuild the widget.info Note
To kick off the animation, you need to call pump()
once (with no duration specified) to start the ticker.
Without it, the animation does not start.These methods provide fine-grained control over the build lifecycle,
which is particularly useful while testing.<topic_end>
<topic_start>
5. Search for our widget using a Finder
With a widget in the test environment, search
through the widget tree for the title and message
Text widgets using a Finder. This allows verification that
the widgets are being displayed correctly.For this purpose, use the top-level find()
method provided by the flutter_test package to create the Finders.
Since you know you’re looking for Text widgets, use the
find.text() method.For more information about Finder classes, see the
Finding widgets in a widget test recipe.
<code_start>void main() {
testWidgets('MyWidget has a title and message', (tester) async {
await tester.pumpWidget(const MyWidget(title: 'T', message: 'M'));
// Create the Finders.