Testing

In this section we will cover how to run tests and develop them. See more on testing principles here.

🧪 Run tests

Standard run

npm run test

Coverage run

Run test and generate coverage, there will be a coverage folder under Electron/. Open index.html file to get an UI for visualizing coverage.

npm run test:coverage

Standalone test run

Go to the test file folder. (The cwd has to be the same as the test file)

npx jest filename.test.tsx

Debug run VSCODE

In debug section launch Debug Jest Tests. This will run all the tests and will stop the execution on any provided breakpoints

👷‍♂️ Develop tests

Test interface result

For debugging the state of the interface we'll be using Jest Preview. This package will help us preview the state of the interface in certain point after the test finished running.

First launch Jest preview server:

npx jest-preview

An output with the port should be logged. Launch a browser instance and go to localhost:3336 or the output port shown after running the command:

Jest Preview Server listening on port 3336

Select the state of the code that you want to preview and add debug() statement:

import { debug } from 'jest-preview'; // ---> Import this line to the test file

test('renders the component and displays title and form', async () => {
    await act(async () => {
      render(
        <StartMenu
          setIsLogged={setIsLoggedMock}
          setIsSigningUp={setIsSigningUpMock}
        />,
      );
    });

    expect(screen.getByText('Spotify Electron')).toBeInTheDocument();
    expect(
      screen.getByText('Inicia sesión en Spotify Electron'),
    ).toBeInTheDocument();
    expect(screen.getByText('Nombre de usuario')).toBeInTheDocument();
    expect(screen.getByText('Contraseña')).toBeInTheDocument();

    debug() // ---> Add this statement, the browser will reflect the state of the UI in this point
  });

Run tests and go to the previously opened browser instance and check the state of the UI in the last debug statement.

Mock Fetch

Every request has to be mocked manually for the test to interactuate with real data. The following code snippet can be used as a mock template for fetch requests:

global.fetch = jest.fn(async (url: string) => {
    if (url === `${Global.backendBaseUrl}/genres/`) {
      return Promise.resolve({
        json: () => JSON.stringify({ Rock: 'Rock', Pop: 'Pop' }),
        status: 200,
        ok: true,
        headers: getMockHeaders(),
      }).catch((error) => {
        console.log(error);
      });
    }
  }) as jest.Mock;

Note that there's two fields included in the response that can be useful/necessary in some situations:

-headers: inserts application/json headers so if they're accessed the test run doesn't crash. -ok: if frontend is checking response.ok. (not used anymore)

Global set up for tests

If it´s necessary to run a script before any test execution you can specify it in package.jsonfile under jest section:

"setupFiles": [
      "./.erb/scripts/check-build-exists.ts","./src/utils/loadOpenApiTests.ts"
    ],