Question

In order to locate Widgets in a test environment, we need to use Finder classes. While it’s possible to write our own Finder classes, it’s generally more convenient to locate Widgets using the tools provided by the flutter_test package.

In this recipe, we’ll look at the find constant provided by the flutter_test package and demonstrate how to work with some of the Finders it provides. For a full list of available finders, please consult the CommonFinders documentation.

If you’re unfamiliar with Widget testing and the role of Finder classes, review the Introduction to widget testing recipe.

Directions

1. Find a Text Widget
2. Find a Widget with a specific Key
3. Find a specific Widget instance

1. Find a Text Widget

In our tests, we often need to find Widgets that contain specific text. This is exactly what the find.text method is for. It will create a Finder that searches for Widgets that display a specific String of text.

testWidgets('finds a Text Widget', (WidgetTester tester) async {
  // Build an App with a Text Widget that displays the letter 'H'
  await tester.pumpWidget(MaterialApp(
    home: Scaffold(
      body: Text('H'),
    ),
  ));

  // Find a Widget that displays the letter 'H'
  expect(find.text('H'), findsOneWidget);
});

2. Find a Widget with a specific Key

In some cases, we may want to find a Widget based on the Key that has been provided to it. This can be handy if we’re displaying multiple instances of the same Widget. For example, we might have a ListView that displays several Text Widgets that contain the same text.

In this case, we can provide a Key to each Widget in the list. This will allow us to uniquely identify a specific Widget, making it easier to find the Widget in the test environment.

testWidgets('finds a Widget using a Key', (WidgetTester tester) async {
  // Define our test key
  final 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);
});

3. Find a specific Widget instance

Finally, we 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 we want to ensure we’re rendering the child Widget.

testWidgets('finds a specific instance', (WidgetTester tester) async {
  final childWidget = Padding(padding: EdgeInsets.zero);

  // Provide our 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);
});

Summary

The find constant provided by the flutter_test package gives us 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, please see the CommonFinders documentation to review all available methods.

Complete example

import 'package:flutter/material.dart';
import 'package:flutter_test/flutter_test.dart';

void main() {
  testWidgets('finds a Text Widget', (WidgetTester tester) async {
    // Build an App with a Text Widget that displays the letter 'H'
    await tester.pumpWidget(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', (WidgetTester tester) async {
    // Define our test key
    final 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', (WidgetTester tester) async {
    final childWidget = Padding(padding: EdgeInsets.zero);

    // Provide our 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);
  });
}