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Mock Mirror

Mock services behind your backend during integration tests.

Install

Install Mock Mirror as a dev dependency:

npm install -D mock-mirror

Why

When writing integration tests, there are numerous ways to mock responses from your backend. This can be done directly in your tests (for example, in Playwright, Cypress, etc.) or by using tools like Mock Service Worker.

But what if your backend connects to other services and you would like to test your frontend and backend together while mocking those service responses?

With Mock Mirror you get a tiny prgrammable server which can be fed with mocks directly within your tests.

Example

describe('user', () => {
  it('should be able to fetch users from the user service', async ({ page }) => {
    await mockMirror(async ({ addRoutes, scope }) => {
      // Add a route to mock the user service
      await addRoutes([
        {
          pathPattern: '/api/users/*',
          response: {
            id: 777,
            username: 'johnwick',
            firstname: 'John',
            lastname: 'Wick',
          },
        },
      ]);

      // This will hit the backend, which will then connect to the mocked user service
      await page.goto('http://localhost:3000/user/detail/777');

      await expect(page.getByText('Welcome, John Wick')).toBeVisible();
    });
  });
});

Development

To start the development server run:

bun run dev