testing-standards

Testing Standards

Follow these standards when writing tests for MCP DevTools packages:

@file packages//src/**/.test.ts @file .cursor/rules/typescript-style.mdc

Test Structure

import {
  describe,
  it,
  expect,
  beforeEach,
  afterEach,
  jest,
} from "@jest/globals";
import { featureUnderTest } from "../path/to/feature";

describe("Feature Name", () => {
  // Setup mocks and test fixtures
  beforeEach(() => {
    // Setup code
  });

  afterEach(() => {
    // Cleanup code
    jest.resetAllMocks();
  });

  describe("Specific Functionality", () => {
    it("should behave as expected in normal conditions", async () => {
      // Arrange
      const input = {
        /* test data */
      };

      // Act
      const result = await featureUnderTest(input);

      // Assert
      expect(result).toEqual(/* expected output */);
    });

    it("should handle error cases appropriately", async () => {
      // Arrange
      const invalidInput = {
        /* invalid test data */
      };

      // Act & Assert
      await expect(featureUnderTest(invalidInput)).rejects.toThrow();
    });
  });
});

Testing Guidelines

1. Test Organization

   • Use descriptive describe and it blocks
   • Group related tests together
   • Follow the Arrange-Act-Assert pattern
   • Keep tests focused on a single functionality

2. Mocking

   • Mock external dependencies
   • Use jest.mock() for external modules
   • Create dedicated mock factories for complex objects
   • Reset mocks between tests

3. Coverage

   • Aim for >80% code coverage
   • Test happy paths and error paths
   • Include edge cases and boundary conditions
   • Test asynchronous behavior correctly

4. Test Data

   • Use realistic test data
   • Create helper functions for test data generation
   • Avoid test data duplication
   • Keep test data close to tests that use it

5. Assertions

   • Make assertions specific and meaningful
   • Test return values, side effects, and exceptions
   • Use appropriate matchers (toEqual, toBeCalledWith, etc.)
   • Write custom matchers for complex assertions