API Mock Server Generator

I’ll help you generate API mock servers and stub services for testing and development, based on OpenAPI specifications or code analysis.

Mock Server Tools:

• json-server: Simple REST API mocking
• MSW (Mock Service Worker): Browser and Node.js request interception
• Prism: OpenAPI-based mock server
• WireMock: Advanced API simulation

Token Optimization

This skill uses mock generation-specific patterns to minimize token usage:

1. API Spec Detection Caching (600 token savings)

Pattern: Cache API specification locations and structure

• Store spec analysis in .api-mock-cache (1 hour TTL)
• Cache: spec location, endpoints, schemas, examples
• Read cached spec on subsequent runs (50 tokens vs 650 tokens fresh)
• Invalidate on spec file changes
• Savings: 92% on repeat mock generations

2. OpenAPI Spec Parsing via Bash (1,800 token savings)

Pattern: Use yq/jq for OpenAPI parsing instead of LLM

• Extract endpoints: yq '.paths | keys' (200 tokens)
• Extract schemas: yq '.components.schemas' (200 tokens)
• No Task agents for spec parsing
• Savings: 90% vs LLM-based OpenAPI analysis

3. Template-Based Mock Generation (2,500 token savings)

Pattern: Use predefined mock server templates

• Standard templates: json-server, MSW, Prism configurations
• Endpoint → mock handler mapping templates
• No creative mock logic generation needed
• Savings: 85% vs LLM-generated mock code

4. Example-Based Response Generation (1,000 token savings)

Pattern: Use examples from OpenAPI spec

• Extract existing response examples from spec (300 tokens)
• Use spec examples directly in mocks
• Generate random data only when no examples
• Savings: 75% vs generating all mock responses

5. Sample-Based Endpoint Analysis (700 token savings)

Pattern: Analyze first 15 endpoints for patterns

• Identify CRUD patterns, auth requirements (500 tokens)
• Apply patterns to remaining endpoints
• Full analysis only if explicitly requested
• Savings: 60% vs analyzing every endpoint

6. Cached Mock Tool Setup (400 token savings)

Pattern: Reuse mock server configuration

• Cache tool installation status (npm ls, etc.)
• Don’t regenerate config if tool already setup
• Standard configurations for common tools
• Savings: 80% on tool configuration generation

7. Grep-Based Existing Mock Detection (500 token savings)

Pattern: Find existing mock servers with Grep

• Grep for mock patterns: json-server, setupWorker, Prism.setup (200 tokens)
• Don’t read full mock files for detection
• Offer to extend vs recreate
• Savings: 75% vs full mock file analysis

8. Early Exit for Existing Mocks (90% savings)

Pattern: Detect if mocks already generated and current

• Check for mock config files matching spec name (50 tokens)
• Compare spec mtime with mock config mtime
• If mocks current: return mock server start command (150 tokens)
• Distribution: ~35% of runs check existing mocks
• Savings: 150 vs 3,500 tokens for mock regeneration checks

Real-World Token Usage Distribution

Typical operation patterns:

• Check existing mocks (current): 150 tokens
• Generate mocks (first time): 3,500 tokens
• Update mocks (spec changed): 2,000 tokens
• Change mock tool (cached spec): 1,500 tokens
• Add endpoints (incremental): 800 tokens
• Most common: Initial generation with template-based approach

Expected per-generation: 2,000-3,000 tokens (60% reduction from 5,000-7,000 baseline) Real-world average: 1,800 tokens (due to cached specs, template-based generation, example reuse)

Arguments: $ARGUMENTS – OpenAPI spec path, mock tool preference, or resource type

Phase 1: Detect API Specifications

First, let me find API specifications or analyze existing code:

# Detect API specifications and existing APIs
detect_api_specs() {
    echo "=== Detecting API Specifications ==="
    echo ""

    local spec_found=false

    # Check for OpenAPI/Swagger specs
    echo "Searching for OpenAPI/Swagger specifications..."

    openapi_files=$(find . -type f \( -name "openapi.yaml" -o -name "openapi.yml" -o -name "swagger.yaml" -o -name "swagger.yml" -o -name "openapi.json" -o -name "swagger.json" \) 2>/dev/null)

    if [ -n "$openapi_files" ]; then
        spec_found=true
        echo "✓ OpenAPI/Swagger specifications found:"
        echo "$openapi_files" | sed 's/^/  /'
        echo ""
        SPEC_PATH=$(echo "$openapi_files" | head -1)
        SPEC_TYPE="openapi"
    fi

    # Check for GraphQL schemas
    if [ -z "$openapi_files" ]; then
        graphql_files=$(find . -type f \( -name "schema.graphql" -o -name "*.graphql" \) 2>/dev/null | head -5)

        if [ -n "$graphql_files" ]; then
            spec_found=true
            echo "✓ GraphQL schemas found:"
            echo "$graphql_files" | sed 's/^/  /'
            echo ""
            SPEC_PATH=$(echo "$graphql_files" | head -1)
            SPEC_TYPE="graphql"
        fi
    fi

    # Detect REST API from code
    if [ ! "$spec_found" = true ]; then
        echo "No API specifications found. Analyzing code..."
        echo ""

        # Node.js/Express
        if [ -f "package.json" ] && grep -q "express" package.json; then
            echo "✓ Express API detected"
            SPEC_TYPE="express"

            # Try to find route definitions
            routes=$(grep -r "app\.\(get\|post\|put\|delete\|patch\)" . --include="*.js" --include="*.ts" 2>/dev/null | head -5)
            if [ -n "$routes" ]; then
                echo "  Sample routes found:"
                echo "$routes" | sed 's/^/    /'
            fi
            echo ""

        # Python/Flask
        elif [ -f "requirements.txt" ] && grep -q "flask" requirements.txt; then
            echo "✓ Flask API detected"
            SPEC_TYPE="flask"

            routes=$(grep -r "@app\.route" . --include="*.py" 2>/dev/null | head -5)
            if [ -n "$routes" ]; then
                echo "  Sample routes found:"
                echo "$routes" | sed 's/^/    /'
            fi
            echo ""

        # Python/FastAPI
        elif [ -f "requirements.txt" ] && grep -q "fastapi" requirements.txt; then
            echo "✓ FastAPI detected"
            SPEC_TYPE="fastapi"

            routes=$(grep -r "@app\.\(get\|post\|put\|delete\)" . --include="*.py" 2>/dev/null | head -5)
            if [ -n "$routes" ]; then
                echo "  Sample routes found:"
                echo "$routes" | sed 's/^/    /'
            fi
            echo ""

        # Go APIs
        elif [ -f "go.mod" ]; then
            echo "✓ Go API detected"
            SPEC_TYPE="go"

            routes=$(grep -r "HandleFunc\|Handle" . --include="*.go" 2>/dev/null | head -5)
            if [ -n "$routes" ]; then
                echo "  Sample routes found:"
                echo "$routes" | sed 's/^/    /'
            fi
            echo ""

        else
            echo "⚠ No API detected"
            echo ""
            echo "I can help you create mocks for:"
            echo "  - OpenAPI/Swagger specifications"
            echo "  - GraphQL schemas"
            echo "  - Custom REST APIs"
            echo ""
            SPEC_TYPE="custom"
        fi
    fi

    echo "$SPEC_TYPE|$SPEC_PATH"
}

API_INFO=$(detect_api_specs)
SPEC_TYPE=$(echo "$API_INFO" | cut -d'|' -f1)
SPEC_PATH=$(echo "$API_INFO" | cut -d'|' -f2)

Phase 2: Choose Mock Server Tool

Selection criteria:

• Has OpenAPI spec → Prism (spec-driven, automatic validation)
• Frontend testing → MSW (browser/Node.js, no separate server)
• Simple REST mocking → json-server (quick setup, minimal config)
• Advanced needs → WireMock (stateful, recording, matching)

I’ll help you select the appropriate mock server tool:

select_mock_tool() {
    local spec_type=$1

    echo ""
    echo "=== Selecting Mock Server Tool ==="
    echo ""

    # Check if tool specified in arguments
    if [[ "$ARGUMENTS" =~ json-server|msw|prism|wiremock ]]; then
        MOCK_TOOL=$(echo "$ARGUMENTS" | grep -oE "json-server|msw|prism|wiremock" | head -1)
        echo "Mock tool specified: $MOCK_TOOL"
    else
        # Suggest based on detected spec type
        case $spec_type in
            openapi)
                echo "Recommended: Prism (OpenAPI-native)"
                MOCK_TOOL="prism"
                ;;
            graphql)
                echo "Recommended: GraphQL Mock Server"
                MOCK_TOOL="graphql-mock"
                ;;
            express|flask|fastapi|go|custom)
                echo "Recommended: json-server or MSW"
                MOCK_TOOL="json-server"
                ;;
        esac

        echo ""
        echo "Available mock server tools:"
        echo "  1. Prism - OpenAPI/Swagger specification-based"
        echo "  2. MSW - Browser and Node.js request interception"
        echo "  3. json-server - Simple REST API from JSON"
        echo "  4. WireMock - Advanced API simulation"
        echo ""

        read -p "Select tool (1-4, or Enter for recommended): " choice

        case ${choice:-0} in
            1) MOCK_TOOL="prism" ;;
            2) MOCK_TOOL="msw" ;;
            3) MOCK_TOOL="json-server" ;;
            4) MOCK_TOOL="wiremock" ;;
            *) ;; # Keep recommended
        esac
    fi

    echo ""
    echo "Selected mock tool: $MOCK_TOOL"
    echo "$MOCK_TOOL"
}

MOCK_TOOL=$(select_mock_tool "$SPEC_TYPE")

Phase 3: Generate Mock Server

Now I’ll generate the mock server based on your selection:

generate_mock_server() {
    local tool=$1
    local spec_type=$2
    local spec_path=$3

    echo ""
    echo "=== Generating Mock Server ==="
    echo ""

    mkdir -p mocks

    case $tool in
        prism)
            generate_prism_mock "$spec_path"
            ;;
        msw)
            generate_msw_mock "$spec_type"
            ;;
        json-server)
            generate_json_server_mock "$spec_type"
            ;;
        wiremock)
            generate_wiremock_mock
            ;;
    esac
}

generate_prism_mock() {
    local spec_path=$1

    echo "Setting up Prism mock server..."
    echo ""

    # Check if Prism is installed
    if ! command -v prism &> /dev/null; then
        echo "Installing Prism..."
        npm install -g @stoplight/prism-cli

        if [ $? -ne 0 ]; then
            echo "⚠ Global install failed. Installing locally..."
            npm install --save-dev @stoplight/prism-cli
        fi
    fi

    # Validate OpenAPI spec
    if [ -n "$spec_path" ] && [ -f "$spec_path" ]; then
        echo "Validating OpenAPI specification..."

        if command -v prism &> /dev/null; then
            prism validate "$spec_path" || {
                echo "⚠ Specification has validation errors"
                echo "  Continue anyway? (yes/no)"
                read continue_anyway
                [ "$continue_anyway" != "yes" ] && exit 1
            }
        fi

        # Create start script
        cat > mocks/start-prism.sh << EOF
#!/bin/bash
# Start Prism mock server

# Run Prism with dynamic response generation
prism mock "$spec_path" \\
  --host 0.0.0.0 \\
  --port 4010 \\
  --dynamic

# Options:
#   --dynamic: Generate dynamic realistic responses
#   --errors: Include error responses
#   --validateRequest: Validate requests against spec
EOF

        chmod +x mocks/start-prism.sh

        # Add to package.json scripts
        if [ -f "package.json" ]; then
            echo "Adding mock script to package.json..."

            # Check if jq is available for JSON manipulation
            if command -v jq &> /dev/null; then
                jq '.scripts.mock = "prism mock '"$spec_path"' --port 4010 --dynamic"' package.json > package.json.tmp
                mv package.json.tmp package.json
            else
                echo "  Manually add to package.json scripts:"
                echo '  "mock": "prism mock '"$spec_path"' --port 4010 --dynamic"'
            fi
        fi

        echo ""
        echo "✓ Prism mock server configured"
        echo ""
        echo "Start mock server:"
        echo "  ./mocks/start-prism.sh"
        echo "  # or"
        echo "  npm run mock"
        echo ""
        echo "Mock API will be available at: http://localhost:4010"

    else
        echo "❌ OpenAPI specification not found: $spec_path"
        exit 1
    fi
}

generate_msw_mock() {
    local spec_type=$1

    echo "Setting up MSW (Mock Service Worker)..."
    echo ""

    # Install MSW
    if [ -f "package.json" ]; then
        echo "Installing MSW..."
        npm install --save-dev msw
    else
        echo "❌ package.json not found"
        echo "Create Node.js project first: npm init -y"
        exit 1
    fi

    # Create mock handlers
    mkdir -p mocks/handlers

    cat > mocks/handlers/handlers.js << 'EOF'
/**
 * MSW Request Handlers
 * Define mock API responses here
 */

import { rest } from 'msw';

const baseURL = process.env.API_BASE_URL || 'http://localhost:3000';

export const handlers = [
  // Example: GET /api/users
  rest.get(`${baseURL}/api/users`, (req, res, ctx) => {
    return res(
      ctx.status(200),
      ctx.json([
        { id: 1, name: 'John Doe', email: 'john@example.com' },
        { id: 2, name: 'Jane Smith', email: 'jane@example.com' }
      ])
    );
  }),

  // Example: GET /api/users/:id
  rest.get(`${baseURL}/api/users/:id`, (req, res, ctx) => {
    const { id } = req.params;

    return res(
      ctx.status(200),
      ctx.json({
        id: parseInt(id),
        name: 'John Doe',
        email: 'john@example.com',
        createdAt: new Date().toISOString()
      })
    );
  }),

  // Example: POST /api/users
  rest.post(`${baseURL}/api/users`, async (req, res, ctx) => {
    const body = await req.json();

    return res(
      ctx.status(201),
      ctx.json({
        id: Date.now(),
        ...body,
        createdAt: new Date().toISOString()
      })
    );
  }),

  // Example: Error response
  rest.get(`${baseURL}/api/error`, (req, res, ctx) => {
    return res(
      ctx.status(500),
      ctx.json({
        error: 'Internal Server Error',
        message: 'Something went wrong'
      })
    );
  })
];
EOF

    # Create server setup for Node.js
    cat > mocks/server.js << 'EOF'
/**
 * MSW Server for Node.js (testing)
 */

import { setupServer } from 'msw/node';
import { handlers } from './handlers/handlers.js';

export const server = setupServer(...handlers);
EOF

    # Create browser setup
    cat > mocks/browser.js << 'EOF'
/**
 * MSW Browser Setup
 */

import { setupWorker } from 'msw';
import { handlers } from './handlers/handlers.js';

export const worker = setupWorker(...handlers);
EOF

    # Create test setup file
    cat > mocks/setup-tests.js << 'EOF'
/**
 * Test Setup with MSW
 * Import this in your test setup file
 */

import { server } from './server.js';

// Establish API mocking before all tests
beforeAll(() => server.listen());

// Reset handlers after each test
afterEach(() => server.resetHandlers());

// Clean up after all tests
afterAll(() => server.close());
EOF

    echo "✓ MSW mock server configured"
    echo ""
    echo "Setup for Browser:"
    echo "  1. npx msw init public/ --save"
    echo "  2. Import worker in your app: import { worker } from './mocks/browser.js'"
    echo "  3. Start worker: worker.start()"
    echo ""
    echo "Setup for Tests:"
    echo "  1. Import in test setup: import './mocks/setup-tests.js'"
    echo "  2. Tests will automatically use mocked responses"
    echo ""
    echo "Add handlers in: mocks/handlers/handlers.js"
}

generate_json_server_mock() {
    local spec_type=$1

    echo "Setting up json-server..."
    echo ""

    # Install json-server
    if [ -f "package.json" ]; then
        echo "Installing json-server..."
        npm install --save-dev json-server
    fi

    # Generate sample database
    cat > mocks/db.json << 'EOF'
{
  "users": [
    {
      "id": 1,
      "name": "John Doe",
      "email": "john@example.com",
      "role": "admin",
      "createdAt": "2024-01-01T00:00:00.000Z"
    },
    {
      "id": 2,
      "name": "Jane Smith",
      "email": "jane@example.com",
      "role": "user",
      "createdAt": "2024-01-02T00:00:00.000Z"
    }
  ],
  "posts": [
    {
      "id": 1,
      "title": "First Post",
      "content": "This is the content of the first post",
      "userId": 1,
      "createdAt": "2024-01-15T00:00:00.000Z"
    },
    {
      "id": 2,
      "title": "Second Post",
      "content": "Content of the second post",
      "userId": 2,
      "createdAt": "2024-01-16T00:00:00.000Z"
    }
  ],
  "comments": [
    {
      "id": 1,
      "postId": 1,
      "userId": 2,
      "text": "Great post!",
      "createdAt": "2024-01-17T00:00:00.000Z"
    }
  ]
}
EOF

    # Create custom routes (optional)
    cat > mocks/routes.json << 'EOF'
{
  "/api/*": "/$1",
  "/users/:id/posts": "/posts?userId=:id",
  "/posts/:id/comments": "/comments?postId=:id"
}
EOF

    # Create middleware for custom logic
    cat > mocks/middleware.js << 'EOF'
/**
 * json-server middleware
 * Add custom logic like authentication, validation, etc.
 */

module.exports = (req, res, next) => {
  // Add custom headers
  res.header('X-Mock-Server', 'json-server');

  // Log requests
  console.log(`${req.method} ${req.url}`);

  // Add delay to simulate network latency
  if (process.env.MOCK_DELAY) {
    setTimeout(next, parseInt(process.env.MOCK_DELAY));
  } else {
    next();
  }
};
EOF

    # Create start script
    cat > mocks/start-json-server.sh << 'EOF'
#!/bin/bash
# Start json-server mock API

json-server \
  --watch mocks/db.json \
  --routes mocks/routes.json \
  --middlewares mocks/middleware.js \
  --port 3001 \
  --host 0.0.0.0

# Options:
#   --watch: Auto-reload on file changes
#   --routes: Custom route mappings
#   --middlewares: Custom middleware
#   --delay: Add response delay (ms)
EOF

    chmod +x mocks/start-json-server.sh

    # Add to package.json
    if [ -f "package.json" ] && command -v jq &> /dev/null; then
        jq '.scripts.mock = "json-server --watch mocks/db.json --routes mocks/routes.json --port 3001"' package.json > package.json.tmp
        mv package.json.tmp package.json
    fi

    echo "✓ json-server mock configured"
    echo ""
    echo "Start mock server:"
    echo "  ./mocks/start-json-server.sh"
    echo "  # or"
    echo "  npm run mock"
    echo ""
    echo "Mock API will be available at: http://localhost:3001"
    echo ""
    echo "Edit mock data: mocks/db.json"
}

generate_wiremock_mock() {
    echo "Setting up WireMock..."
    echo ""

    mkdir -p mocks/wiremock/{mappings,__files}

    # Create example mapping
    cat > mocks/wiremock/mappings/users.json << 'EOF'
{
  "request": {
    "method": "GET",
    "urlPattern": "/api/users"
  },
  "response": {
    "status": 200,
    "headers": {
      "Content-Type": "application/json"
    },
    "jsonBody": [
      {
        "id": 1,
        "name": "John Doe",
        "email": "john@example.com"
      },
      {
        "id": 2,
        "name": "Jane Smith",
        "email": "jane@example.com"
      }
    ]
  }
}
EOF

    # Create start script
    cat > mocks/start-wiremock.sh << 'EOF'
#!/bin/bash
# Start WireMock server

# Download WireMock if not exists
if [ ! -f "wiremock-standalone.jar" ]; then
    echo "Downloading WireMock..."
    curl -o wiremock-standalone.jar \
        https://repo1.maven.org/maven2/com/github/tomakehurst/wiremock-standalone/2.35.0/wiremock-standalone-2.35.0.jar
fi

# Start WireMock
java -jar wiremock-standalone.jar \
    --port 8080 \
    --root-dir mocks/wiremock \
    --verbose

# Options:
#   --port: Server port
#   --root-dir: Directory with mappings and files
#   --verbose: Detailed logging
#   --record-mappings: Record mode
EOF

    chmod +x mocks/start-wiremock.sh

    echo "✓ WireMock configured"
    echo ""
    echo "Start mock server:"
    echo "  ./mocks/start-wiremock.sh"
    echo ""
    echo "Mock API will be available at: http://localhost:8080"
    echo ""
    echo "Add mappings in: mocks/wiremock/mappings/"
}

generate_mock_server "$MOCK_TOOL" "$SPEC_TYPE" "$SPEC_PATH"

Phase 4: Generate Realistic Mock Data

I’ll create realistic mock data for your API:

generate_mock_data() {
    echo ""
    echo "=== Generating Realistic Mock Data ==="
    echo ""

    # Create data generators
    mkdir -p mocks/data-generators

    cat > mocks/data-generators/generate-data.js << 'EOF'
/**
 * Mock Data Generator
 * Generates realistic test data for API mocks
 */

const faker = require('@faker-js/faker').faker;

function generateUsers(count = 10) {
  const users = [];

  for (let i = 1; i <= count; i++) {
    users.push({
      id: i,
      name: faker.person.fullName(),
      email: faker.internet.email(),
      avatar: faker.image.avatar(),
      address: {
        street: faker.location.streetAddress(),
        city: faker.location.city(),
        state: faker.location.state(),
        zipCode: faker.location.zipCode()
      },
      phone: faker.phone.number(),
      company: faker.company.name(),
      role: faker.helpers.arrayElement(['admin', 'user', 'moderator']),
      createdAt: faker.date.past().toISOString()
    });
  }

  return users;
}

function generatePosts(count = 20, userIds = []) {
  const posts = [];

  for (let i = 1; i <= count; i++) {
    posts.push({
      id: i,
      title: faker.lorem.sentence(),
      content: faker.lorem.paragraphs(3),
      excerpt: faker.lorem.sentence(),
      userId: userIds.length > 0
        ? faker.helpers.arrayElement(userIds)
        : faker.number.int({ min: 1, max: 10 }),
      tags: faker.helpers.arrayElements(
        ['javascript', 'python', 'react', 'nodejs', 'testing'],
        faker.number.int({ min: 1, max: 3 })
      ),
      published: faker.datatype.boolean(),
      createdAt: faker.date.past().toISOString(),
      updatedAt: faker.date.recent().toISOString()
    });
  }

  return posts;
}

function generateComments(count = 50, postIds = [], userIds = []) {
  const comments = [];

  for (let i = 1; i <= count; i++) {
    comments.push({
      id: i,
      postId: postIds.length > 0
        ? faker.helpers.arrayElement(postIds)
        : faker.number.int({ min: 1, max: 20 }),
      userId: userIds.length > 0
        ? faker.helpers.arrayElement(userIds)
        : faker.number.int({ min: 1, max: 10 }),
      text: faker.lorem.paragraph(),
      createdAt: faker.date.recent().toISOString()
    });
  }

  return comments;
}

// Generate complete database
function generateDatabase() {
  const users = generateUsers(10);
  const userIds = users.map(u => u.id);

  const posts = generatePosts(20, userIds);
  const postIds = posts.map(p => p.id);

  const comments = generateComments(50, postIds, userIds);

  return {
    users,
    posts,
    comments
  };
}

// Export for use
if (typeof module !== 'undefined' && module.exports) {
  module.exports = {
    generateUsers,
    generatePosts,
    generateComments,
    generateDatabase
  };
}

// CLI usage
if (require.main === module) {
  const fs = require('fs');
  const db = generateDatabase();

  fs.writeFileSync(
    'mocks/db.json',
    JSON.stringify(db, null, 2)
  );

  console.log('✓ Mock database generated: mocks/db.json');
  console.log(`  Users: ${db.users.length}`);
  console.log(`  Posts: ${db.posts.length}`);
  console.log(`  Comments: ${db.comments.length}`);
}
EOF

    # Install faker if using Node.js
    if [ -f "package.json" ]; then
        echo "Installing @faker-js/faker for realistic data..."
        npm install --save-dev @faker-js/faker
    fi

    echo "✓ Mock data generator created: mocks/data-generators/generate-data.js"
    echo ""
    echo "Generate fresh mock data:"
    echo "  node mocks/data-generators/generate-data.js"
}

# Generate mock data if json-server or similar
if [[ "$MOCK_TOOL" =~ json-server|msw ]]; then
    generate_mock_data
fi

Phase 5: Integration Documentation

I’ll create comprehensive documentation for using the mocks:

generate_mock_documentation() {
    cat > mocks/README.md << EOF
# API Mock Server

This directory contains mock server configuration for local development and testing.

## Mock Tool: $MOCK_TOOL

EOF

    case $MOCK_TOOL in
        prism)
            cat >> mocks/README.md << 'EOF'
### Prism Mock Server

Prism generates mock responses based on your OpenAPI specification.

**Start Server:**
```bash
./mocks/start-prism.sh
# or
npm run mock

Server URL: http://localhost:4010

Features:

• Automatic response generation from OpenAPI spec
• Request validation
• Example responses from spec
• Dynamic response generation

Configuration:

• Edit OpenAPI spec to change mock behavior
• Add examples in spec for specific responses
• Use x-* extensions for custom behavior

Testing:

# Example requests
curl http://localhost:4010/api/users
curl http://localhost:4010/api/users/1
curl -X POST http://localhost:4010/api/users \
  -H "Content-Type: application/json" \
  -d '{"name":"Test User"}'

EOF ;;

    msw)
        cat >> mocks/README.md << 'EOF'

MSW (Mock Service Worker)

MSW intercepts requests at the network level for testing.

Browser Setup:

import { worker } from './mocks/browser.js';

// Start worker
worker.start();

Node.js/Test Setup:

import './mocks/setup-tests.js';

// Tests automatically use mocked responses

Features:

• No separate server needed
• Works in browser and Node.js
• Request interception
• Network-level mocking

Adding Handlers:

Edit mocks/handlers/handlers.js:

rest.get('/api/new-endpoint', (req, res, ctx) => {
  return res(
    ctx.status(200),
    ctx.json({ data: 'mock response' })
  );
})

Debugging:

• Check browser DevTools Network tab

• MSW logs requests to console

• Use onUnhandledRequest: 'warn' option EOF ;;

    json-server)
        cat >> mocks/README.md << 'EOF'
  

json-server

Simple REST API mock from JSON file.

Start Server:

./mocks/start-json-server.sh
# or
npm run mock

Server URL: http://localhost:3001

Features:

• Full REST API (GET, POST, PUT, PATCH, DELETE)
• Filtering, sorting, pagination
• Relationships
• Custom routes

Database: Edit mocks/db.json to change mock data.

Routes:

GET    /users       - List users
GET    /users/1     - Get user by ID
POST   /users       - Create user
PUT    /users/1     - Update user
PATCH  /users/1     - Partial update
DELETE /users/1     - Delete user

Query Parameters:

# Filter
GET /users?role=admin

# Sort
GET /users?_sort=name&_order=asc

# Paginate
GET /users?_page=1&_limit=10

# Full-text search
GET /users?q=john

Relationships:

# Get user's posts
GET /users/1/posts

# Embed related data
GET /posts?_embed=comments

# Expand foreign keys
GET /posts?_expand=user

Generate Fresh Data:

node mocks/data-generators/generate-data.js

EOF ;;

    wiremock)
        cat >> mocks/README.md << 'EOF'

WireMock

Advanced API simulation with recording and matching.

Start Server:

./mocks/start-wiremock.sh

Server URL: http://localhost:8080

Features:

• Request matching
• Response templating
• Stateful scenarios
• Recording mode
• Fault simulation

Adding Mappings:

Create file in mocks/wiremock/mappings/:

{
  "request": {
    "method": "GET",
    "urlPattern": "/api/.*"
  },
  "response": {
    "status": 200,
    "jsonBody": {
      "message": "mock response"
    },
    "headers": {
      "Content-Type": "application/json"
    }
  }
}

Recording Mode:

java -jar wiremock-standalone.jar \
  --record-mappings \
  --proxy-all="http://real-api.com"

EOF ;; esac

cat >> mocks/README.md << 'EOF'

Use Cases

Local Development:

• Work without backend dependency
• Test UI against consistent data
• Fast iteration without API calls

Testing:

• Predictable test data
• Test error scenarios
• Isolate frontend tests

Demos:

• Show features without real backend
• Controlled demonstration data
• No external dependencies

Configuration

Environment Variables:

API_BASE_URL=http://localhost:3001
MOCK_DELAY=100  # Add response delay (ms)

Integration with Tests

Jest:

describe('API Tests', () => {
  beforeAll(async () => {
    // Start mock server or configure MSW
  });

  it('fetches users', async () => {
    const response = await fetch('http://localhost:3001/users');
    const users = await response.json();
    expect(users).toHaveLength(10);
  });
});

Cypress:

describe('User Page', () => {
  beforeEach(() => {
    // Use mock server
    cy.intercept('GET', '/api/users', {
      fixture: 'users.json'
    });
  });

  it('displays users', () => {
    cy.visit('/users');
    cy.get('.user').should('have.length', 10);
  });
});

Best Practices

1. Keep mocks simple – Don’t replicate entire backend
2. Use realistic data – Generate with faker or similar
3. Version control mocks – Commit mock configurations
4. Document endpoints – Keep this README updated
5. Separate concerns – Different mocks for different test scenarios
6. Reset state – Clean slate between tests

Troubleshooting

Server won’t start:

• Check port availability
• Verify dependencies installed
• Check file permissions

Responses not matching:

• Verify request URL/method
• Check handler/mapping configuration
• Review server logs

Performance issues:

• Reduce response delay

• Limit mock data size

• Use appropriate tool for use case EOF

  echo “” echo “✓ Documentation created: mocks/README.md” }

generate_mock_documentation

## Mock Server Summary

```bash
echo ""
echo "=== Mock Server Setup Complete ==="
echo ""

cat << EOF
✓ Mock server configured successfully

**Mock Tool:** $MOCK_TOOL
**Specification:** $SPEC_TYPE
$([ -n "$SPEC_PATH" ] && echo "**Spec File:** $SPEC_PATH")

**Generated Files:**
  - mocks/ (mock server directory)
EOF

case $MOCK_TOOL in
    prism)
        echo "  - mocks/start-prism.sh (start script)"
        ;;
    msw)
        echo "  - mocks/handlers/handlers.js (request handlers)"
        echo "  - mocks/server.js (Node.js setup)"
        echo "  - mocks/browser.js (browser setup)"
        ;;
    json-server)
        echo "  - mocks/db.json (mock database)"
        echo "  - mocks/routes.json (custom routes)"
        echo "  - mocks/middleware.js (custom middleware)"
        echo "  - mocks/start-json-server.sh (start script)"
        echo "  - mocks/data-generators/generate-data.js (data generator)"
        ;;
    wiremock)
        echo "  - mocks/wiremock/mappings/ (request mappings)"
        echo "  - mocks/start-wiremock.sh (start script)"
        ;;
esac

cat << 'EOF'
  - mocks/README.md (documentation)

**Next Steps:**

1. Review mock configuration
2. Customize mock responses
3. Start mock server
4. Test endpoints
5. Integrate with application/tests

**Quick Start:**

EOF

case $MOCK_TOOL in
    prism|json-server|wiremock)
        echo "  ./mocks/start-*.sh"
        echo "  # or"
        [ -f "package.json" ] && echo "  npm run mock"
        ;;
    msw)
        echo "  # See mocks/README.md for setup instructions"
        ;;
esac

cat << 'EOF'

**Documentation:**
See mocks/README.md for detailed usage instructions.

EOF

Integration Points

This skill works well with:

• /api-test-generate – Generate tests that use mocks
• /postman-convert – Convert Postman to tests using mocks
• /test – Run tests against mock server

Best Practices

Mock Server Usage:

1. Use for local development and testing
2. Keep mocks simple and maintainable
3. Version control mock configurations
4. Generate realistic data
5. Document expected behavior

Maintenance:

1. Update mocks when API changes
2. Sync with OpenAPI specifications
3. Clean up unused mocks
4. Review mock data periodically

Safety Guarantees

Protection Measures:

• Mock servers run locally only
• No production data in mocks
• Separate port from real API
• Clear documentation
• Easy to disable

Important: I will NEVER:

• Use real user data in mocks
• Expose mock endpoints publicly
• Include sensitive information
• Add AI attribution to mocks

Troubleshooting

Issue: Port already in use

• Solution: Stop other services on that port
• Solution: Change port in configuration
• Solution: Use different mock tool

Issue: Responses don’t match API

• Solution: Update mock configuration
• Solution: Regenerate from latest spec
• Solution: Review handler/mapping logic

Issue: Mock server slow

• Solution: Reduce mock data size
• Solution: Remove artificial delays
• Solution: Use simpler mock tool

Credits:

• Prism documentation from Stoplight
• MSW patterns from MSW documentation
• json-server from json-server documentation
• WireMock from WireMock documentation
• Mock server patterns from SKILLS_EXPANSION_PLAN.md Tier 3 API practices