Vitest Testing

Vitest Testing

Running Tests

# Run all tests
npx vitest run

# Run in watch mode
npx vitest

# Run with coverage
npx vitest run --coverage

# Run a specific test file
npx vitest run src/utils/stats.test.ts

# Run tests matching a pattern
npx vitest run -t "rolling average"

Test File Naming

• Unit tests: <module>.test.ts co-located with the source file
• Integration tests: <feature>.integration.test.ts in a __tests__/ directory

Test Structure

import { describe, it, expect, beforeEach, vi } from 'vitest';

describe('ModuleName', () => {
  describe('functionName', () => {
    it('should describe expected behavior', () => {
      // Arrange
      const input = createTestInput();

      // Act
      const result = functionName(input);

      // Assert
      expect(result).toEqual(expectedOutput);
    });

    it('should handle edge case', () => {
      expect(() => functionName(null)).toThrow('Expected valid input');
    });
  });
});

Best Practices

• Test behavior, not implementation. If internal refactoring breaks tests, the tests are too coupled.
• Use descriptive test names: should calculate rolling AHI average with gaps in data
• Test edge cases: empty arrays, single elements, NaN values, boundary conditions.
• Mock external dependencies (IndexedDB, OPFS, Web Workers) using vi.mock().
• Use beforeEach for setup, not shared mutable state.
• For statistical functions, compare against known values from reference implementations.
• Use toBeCloseTo() for floating-point comparisons.