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<topic_end>
<topic_start>
3. find a specific widget instance
finally, you might be interested in locating a specific instance of a widget.
for example, this can be useful when creating widgets that take a child
property and you want to ensure you’re rendering the child widget.
<code_start>
testWidgets('finds a specific instance', (tester) async {
const childWidget = padding(padding: EdgeInsets.zero);
// provide the childWidget to the container.
await tester.pumpWidget(Container(child: childWidget));
// search for the childWidget in the tree and verify it exists.
expect(find.byWidget(childWidget), findsOneWidget);
});
<code_end>
<topic_end>
<topic_start>
summary
the find constant provided by the flutter_test package provides
several ways to locate widgets in the test environment. this recipe
demonstrated three of these methods, and several more methods exist
for different purposes.
if the above examples do not work for a particular use-case,
see the CommonFinders documentation
to review all available methods.
<topic_end>
<topic_start>
complete example
<code_start>
import 'package:flutter/material.dart';
import 'package:flutter_test/flutter_test.dart';
void main() {
testWidgets('finds a text widget', (tester) async {
// build an app with a text widget that displays the letter 'h'.
await tester.pumpWidget(const MaterialApp(
home: scaffold(
body: Text('H'),
),
));
// find a widget that displays the letter 'h'.
expect(find.text('H'), findsOneWidget);
});
testWidgets('finds a widget using a key', (tester) async {
// define the test key.
const testKey = Key('K');
// build a MaterialApp with the testKey.
await tester.pumpWidget(MaterialApp(key: testKey, home: container()));
// find the MaterialApp widget using the testKey.
expect(find.byKey(testKey), findsOneWidget);
});
testWidgets('finds a specific instance', (tester) async {
const childWidget = padding(padding: EdgeInsets.zero);
// provide the childWidget to the container.
await tester.pumpWidget(Container(child: childWidget));
// search for the childWidget in the tree and verify it exists.
expect(find.byWidget(childWidget), findsOneWidget);
});
}
<code_end>
<topic_end>
<topic_start>
handle scrolling
many apps feature lists of content,
from email clients to music apps and beyond.
to verify that lists contain the expected content
using widget tests,
you need a way to scroll through lists to search for particular items.
to scroll through lists via integration tests,
use the methods provided by the WidgetTester class,
which is included in the flutter_test package:
in this recipe, learn how to scroll through a list of items to
verify a specific widget is being displayed, and discuss the pros on cons of
different approaches.
this recipe uses the following steps:
<topic_end>
<topic_start>
1. create an app with a list of items
this recipe builds an app that shows a long list of items.
to keep this recipe focused on testing, use the app created in the
work with long lists recipe.
if you’re unsure of how to work with long lists,
see that recipe for an introduction.
add keys to the widgets you want to interact with
inside the integration tests.
<code_start>
import 'package:flutter/material.dart';
void main() {
runApp(MyApp(
items: List<String>.generate(10000, (i) => 'item $i'),
));
}
class MyApp extends StatelessWidget {
final List<String> items;
const MyApp({super.key, required this.items});
@override
widget build(BuildContext context) {
const title = 'long list';
return MaterialApp(
title: title,
home: scaffold(