A modern TypeScript CLI tool for mocking backend APIs using YAML files. Perfect for frontend developers who need to simulate backend APIs during development.
/users/:id)npm install -g fake-end
Or use it directly with npx:
npx fake-end run
mock_server directory in your project rootmkdir mock_server
echo "- method: GET
path: /hello
status: 200
body:
message: 'Hello, World!'" > mock_server/hello.yaml
npx fake-end run
Your mock server will be running at http://localhost:4000!
Each YAML file contains an array of endpoint definitions:
- method: GET # HTTP method (GET, POST, PUT, DELETE, PATCH)
path: /users/:id # Route path (supports parameters)
status: 200 # HTTP status code
body: # Response body (can be any valid JSON)
id: ":id"
name: "Mock User"
email: "user@example.com"
delayMs: 150 # Optional delay in milliseconds
Files in nested folders become part of the URL path:
mock_server/
├── users.yaml # Routes: /users/*
├── auth.yaml # Routes: /auth/*
└── api/
└── v1/
└── products.yaml # Routes: /api/v1/products/*
Use :parameter syntax in your paths:
- method: GET
path: /users/:id
status: 200
body:
id: ":id" # Will be replaced with actual parameter
name: "User :id" # Dynamic interpolation
Access request data in your responses:
- method: POST
path: /users
status: 201
body:
name: "{{body.name}}" # From request body
email: "{{body.email}}" # From request body
id: "{{query.generateId}}" # From query parameters
fake-end run [options]
Options:
-p, --port <port> Port to run the server on (default: 4000)
-d, --dir <directory> Directory containing mock YAML files (default: mock_server)
-v, --verbose Enable verbose logging
--no-cache Disable TypeScript interface caching for development
--dynamic-mocks Execute mock functions on each request instead of at startup
-h, --help Display help for command
Generate YAML mock files from cURL commands:
fake-end generate [options]
Options:
-c, --curl <curl> cURL command to analyze and mock
-f, --file <file> File containing cURL command
-o, --output <output> Output directory for generated YAML files (default: mock_server)
--execute Force execution of the cURL command to capture actual response
--no-execute Skip execution and infer response structure instead
--ollama Use Ollama for AI-powered response generation
--ollama-model <model> Ollama model to use (default: qwen2.5-coder:0.5b)
--ollama-host <host> Ollama host URL (default: http://localhost:11434)
-h, --help Display help for command
mock_server/users.yaml:
- method: GET
path: /users
status: 200
body:
- id: "1"
name: "John Doe"
email: "john@example.com"
- id: "2"
name: "Jane Smith"
email: "jane@example.com"
- method: GET
path: /users/:id
status: 200
body:
id: ":id"
name: "User :id"
email: "user:id@example.com"
delayMs: 100
- method: POST
path: /users
status: 201
body:
id: "new-user-id"
name: "{{body.name}}"
email: "{{body.email}}"
message: "User created successfully"
mock_server/auth.yaml:
- method: POST
path: /auth/login
status: 200
body:
token: "mock-jwt-token"
user:
id: "1"
email: "{{body.email}}"
name: "Mock User"
delayMs: 200
- method: POST
path: /auth/register
status: 201
body:
message: "User registered successfully"
user:
id: "new-user-id"
email: "{{body.email}}"
name: "{{body.name}}"
mock_server/api/v1/products.yaml:
- method: GET
path: /products
status: 200
body:
data:
- id: "1"
name: "Product 1"
price: 99.99
pagination:
page: 1
total: 1
- method: GET
path: /products/:id
status: 200
body:
id: ":id"
name: "Product :id"
price: 49.99
This creates endpoints at:
GET /api/v1/productsGET /api/v1/products/:idGenerate YAML mock files directly from cURL commands:
# Generate from a cURL command directly
fake-end generate --curl "curl -X POST https://api.example.com/users -H 'Content-Type: application/json' -d '{\"name\":\"John\",\"email\":\"john@example.com\"}'"
# Generate from a file containing cURL command
echo "curl -X GET https://api.example.com/users/123" > curl-command.txt
fake-end generate --file curl-command.txt
# Force execution to capture real response
fake-end generate --curl "curl -X GET https://api.example.com/users" --execute
# Use AI to generate realistic responses (requires Ollama)
fake-end generate --curl "curl -X GET https://api.example.com/products" --ollama
Fake-End can automatically generate realistic mock data from TypeScript interface definitions:
// types/User.ts
interface User {
id: string;
name: string;
email: string;
age: number;
isActive: boolean;
createdAt: Date;
}
# mock_server/users.yaml
- method: GET
path: /users/:id
status: 200
interfacePath: "./types/User.ts#User" # Points to TypeScript interface
body: {} # Will be auto-generated from interface
The server will automatically generate realistic data matching your TypeScript interface:
{
"id": "a7b2c3d4-e5f6-7a8b-9c0d-1e2f3a4b5c6d",
"name": "Sarah Johnson",
"email": "sarah.johnson@example.com",
"age": 28,
"isActive": true,
"createdAt": "2024-03-15T10:30:00.000Z"
}
Fake-End includes Faker.js integration for generating realistic mock data:
- method: GET
path: /users
status: 200
body:
users: "{{faker.helpers.multiple(faker.helpers.arrayElement([{id: faker.string.uuid(), name: faker.person.fullName(), email: faker.internet.email()}]), {count: 10})}}"
pagination:
total: 100
page: 1
limit: 10
Use Ollama for intelligent response generation based on cURL commands:
# Install and start Ollama first
curl -fsSL https://ollama.ai/install.sh | sh
ollama pull qwen2.5-coder:0.5b
# Generate intelligent mocks
fake-end generate --curl "curl -X GET https://api.example.com/analytics/dashboard" --ollama
The AI will analyze the endpoint and generate contextually appropriate mock responses.
This project uses Bun as the runtime and package manager:
# Install dependencies
bun install
# Development mode
bun run dev
# Start development server
bun run dev run
# Build the project
bun run build
# Run tests
bun test
bun test:unit # Unit tests only
bun test:e2e # End-to-end tests only
# Code quality
bun run lint # Run ESLint
bun run lint:fix # Auto-fix linting issues
bun run tsc # TypeScript compilation
bun run verify # Full verification pipeline
# Run the built version
bun start
Contributions are welcome! Please feel free to submit a Pull Request.
MIT
FAQs
A modern TypeScript CLI tool for mocking backend APIs using YAML files
We found that fake-end demonstrated a not healthy version release cadence and project activity because the last version was released a year ago. It has 1 open source maintainer collaborating on the project.
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