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Testing Your MCP Server

Thorough testing is critical for ensuring your MCP server functions correctly and reliably. This guide covers strategies and tools for testing MCP servers throughout the development lifecycle.

Testing your MCP server​

In this guide, you'll learn how to:

  • Design test strategies - Create comprehensive test plans for your MCP server
  • Implement different test types - Write unit, integration, and end-to-end tests
  • Use testing tools - Leverage specialized tools for MCP server validation
  • Automate testing - Set up continuous integration for ongoing quality assurance
  • Apply best practices - Follow proven testing approaches for AI applications

Why Test MCP Servers?​

Testing Benefits​

Comprehensive testing of your MCP server provides crucial advantages:

  • Reliability - Ensure your server functions correctly in all scenarios
  • Security - Verify authentication and authorization mechanisms
  • Performance - Identify and address bottlenecks before they impact users
  • Maintainability - Make future changes with confidence
  • Compatibility - Validate interactions with different AI models and clients

Testing Levels​

1. Unit Testing​

Unit tests focus on individual components of your MCP server, such as tool functions or resource handlers.

// Example unit test for a weather tool using Jest
test('get_weather tool returns correct data', async () => {
  // Mock dependencies
  const mockWeatherAPI = jest.fn().mockResolvedValue({
    temperature: 72,
    conditions: 'sunny'
  });
  
  // Create test instance with mocked dependencies
  const weatherTool = new WeatherTool({ weatherAPI: mockWeatherAPI });
  
  // Execute the tool
  const result = await weatherTool.execute({ location: 'San Francisco' });
  
  // Verify results
  expect(result).toEqual({
    temperature: 72,
    conditions: 'sunny',
    location: 'San Francisco'
  });
  expect(mockWeatherAPI).toHaveBeenCalledWith('San Francisco');
});

2. Integration Testing​

Integration tests verify that MCP components work together correctly.

// Example integration test for the MCP server
test('MCP server handles tool requests', async () => {
  // Create a test MCP server
  const server = new TestMCPServer({
    tools: [weatherTool, calculatorTool]
  });
  
  // Start the server
  await server.start();
  
  // Create a test client
  const client = new MCPClient({
    serverUrl: server.url
  });
  
  // Test tool listing
  const tools = await client.request({ method: 'tools/list' });
  expect(tools.result).toHaveLength(2);
  
  // Test tool execution
  const result = await client.request({
    method: 'tools/call',
    params: { name: 'get_weather', arguments: { location: 'New York' } }
  });
  
  expect(result.result).toHaveProperty('temperature');
  
  // Stop the server
  await server.stop();
});

3. End-to-End Testing​

End-to-end tests verify the entire system, including AI model interaction.

// Example end-to-end test
test('AI can use weather tool through MCP', async () => {
  // Set up test environment
  const mcpServer = await startMCPServer();
  const aiClient = createAIClientWithMCP(mcpServer.url);
  
  // Send a message that should trigger tool use
  const response = await aiClient.sendMessage(
    "What's the weather like in San Francisco?"
  );
  
  // Verify the response contains weather information
  expect(response.text).toContain('temperature');
  expect(response.text).toContain('San Francisco');
  
  // Clean up
  await mcpServer.stop();
});

Testing Tools​

MCP Testing Toolkit​

TRMX provides several specialized tools for testing MCP servers:

  • MCP Inspector - Interactive UI for manual testing and debugging
  • TRMX Test Runner - Automated test execution for MCP servers
  • MCP Load Tester - Performance and scalability testing
  • Context Simulator - Test context management without real AI models

1. MCP Inspector​

The MCP Inspector is an interactive tool for testing MCP servers:

# Install the MCP Inspector
npm install -g @trmx/mcp-inspector

# Run the inspector
mcp-inspector --server http://localhost:3000

The inspector provides a user interface for:

  • Discovering available tools, resources, and prompts
  • Testing tool calls with various parameters
  • Viewing detailed request and response logs

2. Automated Testing with TRMX Test Runner​

TRMX provides a specialized test runner for MCP servers:

# Install the test runner
npm install -g @trmx/test-runner

# Run tests
trmx-test --server http://localhost:3000 --suite basic

3. Load Testing​

For production-ready MCP servers, load testing is crucial:

# Install the MCP load tester
npm install -g @trmx/load-tester

# Run load test
trmx-load --server http://localhost:3000 --users 100 --duration 60

Test Scenarios​

Essential Test Cases​

Implement these critical test scenarios for your MCP server:

  1. Tool functionality - Verify each tool works with valid and invalid inputs
  2. Context management - Test conversation history persistence and retrieval
  3. Authentication flows - Validate all authentication methods and permissions
  4. Error handling - Ensure graceful responses to various failure scenarios
  5. Performance under load - Test behavior with many concurrent connections
  6. Resource access - Verify data retrieval from configured resources

Tool Testing​

  • Verify each tool handles valid inputs correctly
  • Test error handling with invalid inputs
  • Check performance under various load conditions

Context Management Testing​

  • Verify conversation history is maintained correctly
  • Test context window management strategies
  • Validate context serialization and deserialization

Authentication Testing​

  • Test OAuth flows
  • Verify token validation and refresh
  • Check permission enforcement

Error Handling​

  • Test graceful handling of network failures
  • Verify proper error messages for invalid requests
  • Check timeout handling

Continuous Integration​

Automated Testing Pipeline​

Integrate testing into your development workflow by:

  • Running tests on every commit - Catch issues before they reach production
  • Using test coverage reports - Identify untested code paths
  • Setting quality gates - Prevent merges when tests fail
  • Preserving test artifacts - Save logs and reports for troubleshooting

Integrate MCP testing into your CI/CD pipeline:

# Example GitHub Actions workflow
name: Test MCP Server

on: [push, pull_request]

jobs:
  test:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v2
      - uses: actions/setup-node@v2
        with:
          node-version: '18'
      - run: npm install
      - run: npm run build
      - run: npm run test:unit
      - run: npm run test:integration
      - run: npm run test:e2e

Best Practices​

Testing Best Practices​

Follow these guidelines for effective MCP server testing:

  • Start small - Begin with unit tests before more complex integration tests
  • Mock external services - Test in isolation from third-party dependencies
  • Use realistic data - Create test fixtures that mirror real-world usage
  • Test edge cases - Include unusual inputs and boundary conditions
  • Track performance metrics - Monitor response times and resource usage
  • Automate regression tests - Prevent old bugs from reappearing

Testing Checklist​

Testing Checklist​

Use this checklist to ensure comprehensive testing:

  • All tools have unit tests
  • Integration tests verify server functionality
  • End-to-end tests confirm AI model interaction
  • Authentication flows are tested
  • Error handling is validated
  • Performance is measured under load
  • All tests run in CI pipeline

Next Steps​

Continue Your MCP Journey​

Now that you understand how to test your MCP server: