Integration testing in Flutter - Mini App: Build & Ship

Build: Counter App

A simple counter app where users can increment and reset a counter. Integration test will verify the full flow of incrementing and resetting.

Target UI

+---------------------+
| Counter App         |
+---------------------+
| Count: 0            |
|                     |
| [+] Increment       |
| [Reset] Reset       |
+---------------------+

Display a counter starting at 0

Increment button increases the counter by 1

Reset button sets the counter back to 0

Integration test to tap increment twice and reset once, verifying displayed count

Starter Code

Flutter

import 'package:flutter/material.dart';

void main() {
  runApp(const MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  @override
  Widget build(BuildContext context) {
    return const MaterialApp(
      home: CounterScreen(),
    );
  }
}

class CounterScreen extends StatefulWidget {
  const CounterScreen({super.key});

  @override
  State<CounterScreen> createState() => _CounterScreenState();
}

class _CounterScreenState extends State<CounterScreen> {
  int _count = 0;

  void _increment() {
    setState(() {
      _count++;
    });
  }

  void _reset() {
    setState(() {
      _count = 0;
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: const Text('Counter App')),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            Text('Count: $_count', key: const Key('counterText'), style: const TextStyle(fontSize: 24)),
            const SizedBox(height: 20),
            ElevatedButton(
              key: const Key('incrementButton'),
              onPressed: _increment,
              child: const Text('+ Increment'),
            ),
            const SizedBox(height: 10),
            ElevatedButton(
              key: const Key('resetButton'),
              onPressed: _reset,
              child: const Text('Reset'),
            ),
          ],
        ),
      ),
    );
  }
}

// TODO: Add integration test in test_driver or integration_test folder

Task 1

Task 2

Task 3

Task 4

Task 5

Solution

Flutter

import 'package:flutter/material.dart';
import 'package:flutter_test/flutter_test.dart';
import 'package:integration_test/integration_test.dart';
import 'package:your_app/main.dart' as app;

void main() {
  IntegrationTestWidgetsFlutterBinding.ensureInitialized();

  testWidgets('Counter increments and resets correctly', (WidgetTester tester) async {
    app.main();
    await tester.pumpAndSettle();

    final Finder incrementButton = find.byKey(const Key('incrementButton'));
    final Finder resetButton = find.byKey(const Key('resetButton'));
    final Finder counterText = find.byKey(const Key('counterText'));

    // Initial count should be 0
    expect(find.text('Count: 0'), findsOneWidget);

    // Tap increment twice
    await tester.tap(incrementButton);
    await tester.pumpAndSettle();
    await tester.tap(incrementButton);
    await tester.pumpAndSettle();

    // Verify count is 2
    expect(find.text('Count: 2'), findsOneWidget);

    // Tap reset
    await tester.tap(resetButton);
    await tester.pumpAndSettle();

    // Verify count is 0
    expect(find.text('Count: 0'), findsOneWidget);
  });
}

This integration test uses Flutter's integration_test package to run the full app and simulate user taps.

We start the app, then find the increment and reset buttons by their keys.

We tap the increment button twice and check the counter text updates to 'Count: 2'.

Then we tap the reset button and verify the counter resets to 'Count: 0'.

This test confirms the app's UI and logic work together correctly.

Final Result

Completed Screen

+---------------------+
| Counter App         |
+---------------------+
| Count: 2            |
|                     |
| [+] Increment       |
| [Reset] Reset       |
+---------------------+

User taps '+ Increment' button twice, count increases from 0 to 2

User taps 'Reset' button, count resets to 0

Stretch Goal

Add an integration test to verify the app shows a snackbar message 'Reset done' when reset button is tapped.

💡 Hint

Use ScaffoldMessenger.of(context).showSnackBar in the reset method and check for snackbar text in the test.

Practice

1. What is the main purpose of integration testing in Flutter apps?

easy

A. To test individual functions for correctness

B. To check the app's UI design colors

C. To measure app performance under load

D. To check if different parts of the app work together correctly

Solution

1. Step 1: Understand integration testing goal

   Integration testing focuses on how different parts of the app interact and work together.

2. Step 2: Compare with other test types

   Unit tests check individual functions, performance tests check speed, and UI design tests check visuals.

3. Final Answer:

   To check if different parts of the app work together correctly -> Option D

4. Quick Check:

   Integration testing = check parts working together [OK]

Hint: Integration tests check combined parts, not single functions [OK]

Common Mistakes:

• Confusing integration testing with unit testing
• Thinking it tests only UI colors
• Mixing it up with performance testing

2. Which line correctly initializes integration testing in a Flutter test file?

easy

A. IntegrationTestWidgetsFlutterBinding.ensureInitialized();

B. WidgetsFlutterBinding.ensureInitialized();

C. IntegrationTestBinding.initialize();

D. TestWidgetsBinding.ensureInitialized();

Solution

1. Step 1: Identify the correct binding for integration tests

   The official Flutter integration test package uses IntegrationTestWidgetsFlutterBinding.ensureInitialized() to set up.

2. Step 2: Check other options for correctness

   WidgetsFlutterBinding is for widget tests, not integration tests. Others are incorrect or do not exist.

3. Final Answer:

   IntegrationTestWidgetsFlutterBinding.ensureInitialized(); -> Option A

4. Quick Check:

   Use IntegrationTestWidgetsFlutterBinding for integration tests [OK]

Hint: Use IntegrationTestWidgetsFlutterBinding.ensureInitialized() for integration tests [OK]

Common Mistakes:

• Using WidgetsFlutterBinding instead of IntegrationTestWidgetsFlutterBinding
• Misspelling the method name
• Trying to call a non-existent initialize() method

3. Given this integration test snippet, what will the test check?

final button = find.text('Tap me');
await tester.tap(button);
await tester.pumpAndSettle();
expect(find.text('Tapped!'), findsOneWidget);

medium

A. The test checks if the button is disabled

B. The button labeled 'Tapped!' is tapped and text changes to 'Tap me'

C. The button labeled 'Tap me' is tapped and text changes to 'Tapped!'

D. The test waits but does not tap any button

Solution

1. Step 1: Analyze the tap action

   The test finds a button with text 'Tap me' and taps it.

2. Step 2: Check the expected result

   After tapping and waiting for animations, it expects to find text 'Tapped!' on screen.

3. Final Answer:

   The button labeled 'Tap me' is tapped and text changes to 'Tapped!' -> Option C

4. Quick Check:

   Tap 'Tap me' button, expect 'Tapped!' text [OK]

Hint: Look for tap target text and expected text after tap [OK]

Common Mistakes:

• Confusing which text is tapped and which is expected
• Ignoring await pumpAndSettle() for UI update
• Assuming no tap happens

4. What is wrong with this integration test code snippet?

void main() {
  testWidgets('tap test', (tester) async {
    final binding = IntegrationTestWidgetsFlutterBinding.ensureInitialized();
    final button = find.text('Click');
    await tester.tap(button);
    expect(find.text('Clicked'), findsOneWidget);
  });
}

medium

A. Binding initialization should be outside testWidgets, in main() before tests

B. The find.text selector is incorrect syntax

C. Missing await before tester.tap

D. expect should be called before tap

Solution

1. Step 1: Check binding initialization placement

   IntegrationTestWidgetsFlutterBinding.ensureInitialized() should be called once before all tests, not inside testWidgets.

2. Step 2: Verify other code parts

   find.text syntax is correct, await is used before tap, and expect is correctly after tap.

3. Final Answer:

   Binding initialization should be outside testWidgets, in main() before tests -> Option A

4. Quick Check:

   Initialize binding once before tests [OK]

Hint: Initialize binding once before tests, not inside each test [OK]

Common Mistakes:

• Calling ensureInitialized inside each testWidgets
• Forgetting await before tap
• Misordering expect before tap

5. You want to write an integration test that types 'hello' into a TextField and then taps a button labeled 'Send'. Which sequence correctly performs this in Flutter integration tests?

hard

A. await tester.tap(find.text('Send')); await tester.enterText(find.byType(TextField), 'hello'); await tester.pump();

B. await tester.enterText(find.byType(TextField), 'hello'); await tester.tap(find.text('Send')); await tester.pumpAndSettle();

C. await tester.enterText(find.text('Send'), 'hello'); await tester.tap(find.byType(TextField)); await tester.pumpAndSettle();

D. await tester.tap(find.byType(TextField)); await tester.enterText(find.text('Send'), 'hello'); await tester.pump();

Solution

1. Step 1: Enter text into the TextField

   Use tester.enterText with find.byType(TextField) to type 'hello'.

2. Step 2: Tap the 'Send' button and wait for UI update

   Tap the button found by text 'Send' and call pumpAndSettle() to wait for animations.

3. Final Answer:

   await tester.enterText(find.byType(TextField), 'hello'); await tester.tap(find.text('Send')); await tester.pumpAndSettle(); -> Option B

4. Quick Check:

   Type first, then tap button, then wait [OK]

Hint: Type text first, then tap button, then wait for UI [OK]

Common Mistakes:

• Tapping button before typing text
• Using wrong finder for TextField or button
• Not waiting with pumpAndSettle after tap