API Versioning Testing: How to Test v1, v2, and Deprecated Endpoints Simultaneously

Your API has v1 and v2 running simultaneously. v1 is deprecated but still used by 30% of clients. Here is how to test both versions without maintaining duplicate test suites.

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Versioned Test Structure

// Shared test logic, parameterized by version
const versions = ['v1', 'v2'];
for (const v of versions) {
  test.describe('GET /api/' + v + '/users', () => {
    test('returns user list', async ({ request }) => {
      const res = await request.get('/api/' + v + '/users');
      expect(res.ok()).toBeTruthy();
      const body = await res.json();
      expect(body.users).toBeInstanceOf(Array);
    });
  });
}

// v2-only features
test('v2 supports pagination', async ({ request }) => {
  const res = await request.get('/api/v2/users?page=1&limit=10');
  const body = await res.json();
  expect(body.pagination).toBeDefined();
  expect(body.pagination.page).toBe(1);
});

// v1 deprecation header check
test('v1 returns deprecation warning', async ({ request }) => {
  const res = await request.get('/api/v1/users');
  expect(res.headers()['deprecation']).toBeDefined();
  expect(res.headers()['sunset']).toBeDefined();
});

Backward Compatibility Testing

test('v2 response is superset of v1', async ({ request }) => {
  const v1 = await (await request.get('/api/v1/users/1')).json();
  const v2 = await (await request.get('/api/v2/users/1')).json();
  // All v1 fields must exist in v2
  for (const key of Object.keys(v1)) {
    expect(v2).toHaveProperty(key);
  }
});