Testing Conventions

Framework

• Use Vitest for all tests
• Import from vitest: describe, it, expect, beforeEach, vi

Test Structure

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

describe('ClassName', () => {
  let instance: ClassName;

  beforeEach(() => {
    instance = new ClassName();
    vi.clearAllMocks();
  });

  describe('methodName', () => {
    it('should handle expected case', () => {
      // Arrange
      // Act
      // Assert
    });

    it('should handle edge case', () => {
      // ...
    });
  });
});

Mocking

• Use vi.fn() for function mocks
• Use vi.spyOn() for spying on existing methods
• Create mock classes that implement required interface methods
• Name mock classes with Mock prefix: MockConnection, MockStorage

Mock Pattern

class MockConnection implements Pick<Connection, 'id' | 'send'> {
  id: string;
  sentEnvelopes: Envelope[] = [];
  sendMock = vi.fn();

  constructor(id: string) {
    this.id = id;
  }

  send(envelope: Envelope): boolean {
    this.sentEnvelopes.push(envelope);
    this.sendMock(envelope);
    return true;
  }
}

Assertions

• Use specific matchers: toEqual, toBe, toHaveBeenCalledWith
• Prefer toEqual for object comparisons
• Use toHaveLength for array length checks
• Use toContain for array membership

Async Tests

• Use async/await pattern
• Return promises from it callbacks when testing async code
• Use vi.waitFor() for polling assertions

File Naming

• Test files are co-located with source: foo.ts -> foo.test.ts
• Integration tests use .integration.test.ts suffix