flutter-testing-skill

Files (3)

• SKILL.md
• advanced-patterns.md · reference/
• playbook.md · reference/

SKILL.md (first lines)

# Flutter Testing Skill

You are a senior Flutter developer specializing in testing.

## Step 1 — Test Type

```
├─ "unit test", "business logic", "model test"
│  └─ Unit test: test/ directory, flutter_test package
│
├─ "widget test", "component test", "UI test"
│  └─ Widget test: test/ directory, testWidgets()
│
├─ "integration test", "E2E", "full app test"
│  └─ Integration test: integration_test/ directory
│
├─ "golden test", "snapshot", "visual regression"
│  └─ Golden test: matchesGoldenFile()
│
└─ Ambiguous? → Widget test (most common)
```

## Core Patterns — Dart

### Widget Test (Most Common)

```dart
import 'package:flutter/material.dart';
import 'package:flutter_test/flutter_test.dart';
import 'package:my_app/screens/login_screen.dart';

void main() {
  testWidgets('Login screen shows email and password fields', (WidgetTester tester) async {
    await tester.pumpWidget(const MaterialApp(home: LoginScreen()));

    // Verify fields exist
    expect(find.byType(TextField), findsNWidgets(2));
    expect(find.text('Email'), findsOneWidget);
    expect(find.text('Password'), findsOneWidget);
    expect(find.byType(ElevatedButton), findsOneWidget);
  });

  testWidgets('Login with valid credentials navigates to dashboard', (WidgetTester tester) async {
    await tester.pumpWidget(const MaterialApp(home: LoginScreen()));

    // Enter credentials
    await tester.enterText(find.byKey(const Key('emailField')), 'user@test.com');
    await tester.enterText(find.byKey(const Key('passwordField')), 'password123');

    // Tap login button
    await tester.tap(find.byKey(const Key('loginButton')));
    await tester.pumpAndSettle(); // Wait for animations and navigation

    // Verify navigation
    expect(find.text('Dashboard'), findsOneWidget);
  });

  testWidgets('Shows error for invalid credentials', (WidgetTester tester) async {
    await tester.pumpWidget(const MaterialApp(home: LoginScreen()));

    await tester.enterText(find.byKey(const Key('emailField')), 'wrong@test.com');
    await tester.enterText(find.byKey(const Key('passwordField')), 'wrong');
    await tester.tap(find.byKey(const Key('loginButton')));
    await tester.pumpAndSettle();

    expect(find.text('Invalid credentials'), findsOneWidget);
  });
}
```

### Finder Strategies

```dart
// By Key (best — explicit test identifiers)
find.byKey(const Key('loginButton'))
find.byKey(const ValueKey('email_input'))

// By Type
find.byType(ElevatedButton)
find.byType(TextField)
find.byType(LoginScreen)

// By Text
find.text('Login')
find.textContaining('Welcome')

// By Icon
find.byIcon(Icons.login)

// By Widget predicate
find.byWidgetPredicate((widget) => widget is Text && widget.data!.startsWith('Error'))

// Descendant/Ancestor
find.descendant(of: find.byType(AppBar), matching: find.text('Title'))
find.ancestor(of: find.text('Login'), matching: find.byType(Card))
```

### Actions

```dart
await tester.tap(finder);                    // Tap
await tester.longPress(finder);              // Long press
await tester.enterText(finder, 'text');      // Type text
await tester.drag(finder, const Offset(0, -300));  // Drag/scroll
await tester.fling(finder, const Offset(0, -500), 1000); // Fling/swipe

// CRITICAL: Always pump after actions
await tester.pump();                         // Single frame
await tester.pump(const Duration(seconds: 1)); // Advance time
await tester.pumpAndSettle();                // Wait for animations to finish
```

### Integration Test

```dart
// integration_test/app_test.dart
import 'package:flutter_test/flutter_test.dart';
import 'package:integration_test/integration_test.dart';
import 'package:my_app/main.dart' as app;

From LambdaTest/agent-skills, MIT.

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