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Rules: testing

// Act - Execute the action const result = functionToTest(input);

Affected files​

These rules apply to files matching the following patterns:

  • **/*.test.ts
  • **/*.test.tsx
  • **/*.spec.ts
  • **/*.spec.tsx
  • **/tests/**
  • **/test/**
  • **/__tests__/**

Detailed rules​

Testing Rules

Coverage​

  • IMPORTANT: Minimum 80% coverage on new code
  • Cover critical paths first
  • Do not aim for 100% at the expense of quality

Mocking​

  • IMPORTANT: No mocks except for external dependencies (API, DB)
  • Prefer stubs over full mocks
  • Avoid mocking internal modules
  • Use factories for test data

Edge Cases​

  • YOU MUST test edge cases:
    • null and undefined
    • Empty strings and whitespace
    • Empty arrays
    • Boundary values (0, -1, MAX_INT)
    • Errors and exceptions

Test Structure (AAA)​

describe('ModuleName', () => {
  describe('functionName', () => {
    it('should [expected behavior] when [condition]', () => {
      // Arrange - Prepare the data
      const input = createTestData();

      // Act - Execute the action
      const result = functionToTest(input);

      // Assert - Verify the result
      expect(result).toEqual(expected);
    });
  });
});

Naming Conventions​

  • Descriptive and readable test names
  • Format: should [behavior] when [condition]
  • Group by functionality with describe

Best Practices​

  • Independent tests (no execution order)
  • Deterministic tests (no random without seed)
  • Fast tests (< 100ms per unit test)
  • One test = one logical assertion
  • Readable tests = living documentation

Automatic application​

These rules are automatically applied by Claude during:

  • Reading the matching files
  • Modifying code
  • Suggestions and fixes

See also​