Joker 🃏

Joker Banner

HTTP request mocking for Dart & Flutter. Beyond testing - enable independent frontend development without backend dependencies.

Use Cases

🚀 Independent Development

Build complete features before backend APIs exist:

void main() async {
  if (kDebugMode) {
    setupMockAPIs(); // Only in development
  }
  runApp(MyApp());
}

void setupMockAPIs() {
  Joker.start();
  
  // User authentication
  Joker.stubJson(
    host: 'api.myapp.com',
    path: '/auth/login',
    method: 'POST',
    data: {
      'token': 'dev_token_123',
      'user': {'id': 1, 'name': 'Dev User'}
    },
  );
  
  // Product catalog
  Joker.stubJson(
    host: 'api.myapp.com', 
    path: '/products',
    data: {
      'products': [
        {'id': 1, 'name': 'iPhone 15', 'price': 999},
        {'id': 2, 'name': 'MacBook Pro', 'price': 1999},
      ]
    },
  );
}

🧪 Testing Excellence

Reliable, fast tests with controlled responses:

group('User Profile Tests', () {
  setUp(() => Joker.start());
  tearDown(() => Joker.stop());

  test('loads user profile successfully', () async {
    Joker.stubJson(
      host: 'api.myapp.com',
      path: '/users/123',
      data: {'id': 123, 'name': 'John Doe', 'email': '[email protected]'},
    );

    final profile = await userService.getProfile(123);
    expect(profile.name, equals('John Doe'));
  });

  test('handles network errors gracefully', () async {
    Joker.stubJson(
      host: 'api.myapp.com',
      path: '/users/456', 
      data: {'error': 'User not found'},
      statusCode: 404,
    );

    expect(
      () => userService.getProfile(456), 
      throwsA(isA<UserNotFound>())
    );
  });
});

Key Features

✅ Universal: Works with any HTTP client using HttpClient (http, dio, etc.)
🎯 Smart Matching: Match by host, path, method, or any combination
📦 JSON-First: Built-in JSON response handling
⚡ Full Control: Custom status codes, headers, delays
🏷️ Organized: Named stubs for complex scenarios
🔄 Flexible: One-time or persistent stubs
🚫 Non-Invasive: No changes needed to existing code

Installation

Add to your pubspec.yaml:

dev_dependencies:
  joker: ^0.2.0

📱 Platform Support: This package is designed for native platforms (mobile, desktop, server) where it provides automatic HTTP interception via HttpOverrides.

🌐 For Web or Cross-Platform: Use joker_http or joker_dio which work on all platforms including web.

Quick Start

import 'package:joker/joker.dart';
import 'package:http/http.dart' as http;

// Start intercepting (required)
Joker.start();

// Simple JSON response
Joker.stubJson(
  host: 'api.example.com',
  path: '/users',
  data: {'users': [{'id': 1, 'name': 'Alice'}]},
);

// Your existing code works unchanged!
final response = await http.get(Uri.parse('https://api.example.com/users'));
final users = jsonDecode(response.body)['users'];

// Always stop when done
Joker.stop();

💡 Note: This automatic interception works on native platforms (mobile, desktop, server). For web or cross-platform apps, see joker_http or joker_dio.

Complete API Reference

Core Methods

Method	Purpose
`Joker.start()`	Begin intercepting HTTP requests
`Joker.stop()`	Stop intercepting and clear all stubs
`Joker.stubJson({...})`	Create JSON response stubs
`Joker.stubJsonArray({...})`	Create JSON array response stubs
`Joker.stubText({...})`	Create text response stubs
`Joker.stubJsonFile({...})`	Create JSON stubs from file (async) - Native only
`Joker.removeStub(stub)`	Remove specific stub
`Joker.removeStubsByName(name)`	Remove stubs by name
`Joker.clearStubs()`	Remove all stubs
`Joker.stubs`	Get all registered stubs (read-only)
`Joker.isActive`	Check if Joker is intercepting requests

Stubbing Methods

`stubJson()` - JSON Object Responses

Creates stubs that return JSON objects:

Joker.stubJson(
  host: 'api.example.com',
  path: '/user/profile',
  method: 'GET',
  data: {
    'id': 123,
    'name': 'John Doe', 
    'email': '[email protected]'
  },
  statusCode: 200,
  headers: {'x-api-version': '1.0'},
  delay: Duration(milliseconds: 300),
  name: 'user-profile',
  removeAfterUse: false,
);

`stubJsonArray()` - JSON Array Responses

Creates stubs that return JSON arrays at root level:

Joker.stubJsonArray(
  host: 'api.example.com',
  path: '/posts',
  data: [
    {'id': 1, 'title': 'Post 1', 'author': 'Alice'},
    {'id': 2, 'title': 'Post 2', 'author': 'Bob'},
  ],
  statusCode: 200,
  headers: {'x-total-count': '2'},
);

`stubText()` - Plain Text Responses

Creates stubs that return plain text:

Joker.stubText(
  host: 'api.example.com',
  path: '/health',
  text: 'OK',
  statusCode: 200,
  headers: {'content-type': 'text/plain'},
);

`stubJsonFile()` - Load JSON from File

Note: Only available on native platforms (mobile, desktop, server). Not available on web due to dart:io restrictions.

Creates stubs by loading JSON data from files (async):

await Joker.stubJsonFile(
  host: 'api.example.com',
  path: '/users',
  filePath: 'test/fixtures/users.json',
  statusCode: 200,
  delay: Duration(milliseconds: 500),
);

Common Parameters

All stubbing methods share these parameters:

Parameter	Type	Default	Description
`host`	`String?`	`null`	Host to match (e.g., 'api.example.com')
`path`	`String?`	`null`	Path to match (e.g., '/users')
`method`	`String?`	`null`	HTTP method ('GET', 'POST', etc.)
`statusCode`	`int`	`200`	HTTP status code
`headers`	`Map<String, String>`	`{}`	Response headers
`delay`	`Duration?`	`null`	Artificial response delay
`name`	`String?`	`null`	Stub name for management
`removeAfterUse`	`bool`	`false`	Auto-remove after first match

Method-Specific Parameters

`stubJson()` Parameters

Parameter	Type	Required	Description
`data`	`Map<String, dynamic>`	✅	JSON object to return

`stubJsonArray()` Parameters

Parameter	Type	Required	Description
`data`	`List<Map<String, dynamic>>`	✅	JSON array to return

`stubText()` Parameters

Parameter	Type	Required	Description
`text`	`String`	✅	Plain text content to return

`stubJsonFile()` Parameters

Parameter	Type	Required	Description
`filePath`	`String`	✅	Path to JSON file to load

Stub Management Examples

Basic Stubbing

// Start intercepting
Joker.start();

// Simple JSON response
Joker.stubJson(
  host: 'api.example.com',
  path: '/posts',
  data: {'posts': [{'id': 1, 'title': 'Hello World'}]},
);

// Make request - it will be intercepted
final posts = await apiClient.getPosts();

Advanced Configuration

// POST endpoint with custom response
Joker.stubJson(
  host: 'api.example.com',
  path: '/users',
  method: 'POST',
  data: {'id': 42, 'created': true},
  statusCode: 201,
  headers: {'Location': '/users/42'},
  delay: Duration(milliseconds: 300), // Simulate network latency
);

// Error responses for testing
Joker.stubJson(
  host: 'api.example.com',
  path: '/users/invalid',
  data: {'error': 'Invalid user ID', 'code': 'INVALID_ID'},
  statusCode: 400,
);

Dynamic Stub Management

// Named stubs for organization
final stub = Joker.stubJson(
  host: 'api.example.com',
  path: '/products',
  data: {'products': []},
  name: 'empty-catalog',
);

// Update stub data dynamically
Joker.removeStubsByName('empty-catalog');
Joker.stubJson(
  host: 'api.example.com', 
  path: '/products',
  data: {'products': [{'id': 1, 'name': 'New Product'}]},
  name: 'populated-catalog',
);

// One-time stubs (auto-remove after use)
Joker.stubJson(
  host: 'api.example.com',
  path: '/auth/refresh',
  data: {'token': 'new_token_456'},
  removeAfterUse: true,
);

// Check active stubs
print('Active stubs: ${Joker.stubs.length}');
print('Joker is active: ${Joker.isActive}');

Real-World Development Example

class ApiMockService {
  static void setupDevelopmentMocks() {
    Joker.start();
    
    _setupAuthEndpoints();
    _setupUserEndpoints(); 
    _setupProductEndpoints();
  }
  
  static void _setupAuthEndpoints() {
    // Login success
    Joker.stubJson(
      host: 'api.myshop.com',
      path: '/auth/login',
      method: 'POST', 
      data: {
        'success': true,
        'token': 'eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9...',
        'user': {
          'id': 1, 
          'email': '[email protected]', 
          'role': 'admin'
        }
      },
      name: 'login-success',
    );
  }
  
  static void _setupProductEndpoints() {
    // Product list with pagination
    Joker.stubJson(
      host: 'api.myshop.com',
      path: '/products',
      data: {
        'products': List.generate(20, (i) => {
          'id': i + 1,
          'name': 'Product ${i + 1}',
          'price': (i + 1) * 10.99,
          'image': 'https://picsum.photos/200/200?random=$i'
        }),
        'total': 100,
        'page': 1,
        'hasMore': true,
      },
      delay: Duration(milliseconds: 500), // Realistic loading time
    );
  }
}

Best Practices

Development Workflow

Use kDebugMode to enable mocks only in development
Create realistic mock data that matches your backend schema
Add delays to test loading states and user experience
Use named stubs to swap between different scenarios

Testing

Always call Joker.stop() in tearDown() methods
Clear stubs between tests with Joker.clearStubs()
Test both success and error scenarios
Use removeAfterUse: true for one-time authentication flows

Organization

// Good: Organized by feature
void setupUserMocks() {
  // user-related stubs
}

void setupProductMocks() {
  // product-related stubs
}

void setupPaymentMocks() {
  // payment-related stubs
}

// Good: Environment-specific setup
void setupMocksForTesting() {
  // minimal, predictable data
}

void setupMocksForDemo() {
  // rich, realistic data
}

How It Works

Joker uses Dart's HttpOverrides.global to intercept all HTTP requests made through HttpClient on native platforms. This works transparently with any package that uses the standard Dart HTTP stack:

package:http
package:dio
dart:io HttpClient
Most other HTTP packages

No changes to your existing code required - just start Joker and define your stubs!

Cross-Platform Support

For web or cross-platform applications, use the companion packages:

joker_http - For package:http on all platforms including web
joker_dio - For package:dio on all platforms including web

These packages provide explicit client configuration that works across all platforms.

License

MIT Licensed - see LICENSE for details.

Support the Project

If you find joker helpful for your projects and it has saved you time, consider supporting its development with a coffee!

Every contribution is highly appreciated and motivates me to keep improving the library, adding new features, and providing support.

Joker 🃏

Use Cases

🚀 Independent Development

🧪 Testing Excellence

Key Features

Installation

Quick Start

Complete API Reference

Core Methods

Stubbing Methods

`stubJson()` - JSON Object Responses

`stubJsonArray()` - JSON Array Responses

`stubText()` - Plain Text Responses

`stubJsonFile()` - Load JSON from File

Common Parameters

Method-Specific Parameters

`stubJson()` Parameters

`stubJsonArray()` Parameters

`stubText()` Parameters

`stubJsonFile()` Parameters

Stub Management Examples

Basic Stubbing

Advanced Configuration

Dynamic Stub Management

Real-World Development Example

Best Practices

Development Workflow

Testing

Organization

How It Works

Cross-Platform Support

License

Support the Project

Libraries

joker package

Joker 🃏

Use Cases

🚀 Independent Development

🧪 Testing Excellence

Key Features

Installation

Quick Start

Complete API Reference

Core Methods

Stubbing Methods

stubJson() - JSON Object Responses

stubJsonArray() - JSON Array Responses

stubText() - Plain Text Responses

stubJsonFile() - Load JSON from File

Common Parameters

Method-Specific Parameters

stubJson() Parameters

stubJsonArray() Parameters

stubText() Parameters

stubJsonFile() Parameters

Stub Management Examples

Basic Stubbing

Advanced Configuration

Dynamic Stub Management

Real-World Development Example

Best Practices

Development Workflow

Testing

Organization

How It Works

Cross-Platform Support

License

Support the Project

Libraries

joker package

`stubJson()` - JSON Object Responses

`stubJsonArray()` - JSON Array Responses

`stubText()` - Plain Text Responses

`stubJsonFile()` - Load JSON from File

`stubJson()` Parameters

`stubJsonArray()` Parameters

`stubText()` Parameters

`stubJsonFile()` Parameters