Make every test able to fail

How to do it

Watch each new test fail once before making it pass. Turn on lint rules that catch empty or assertion-free tests, such as vitest/expect-expect or jest/expect-expect. Await every asynchronous assertion.

Example

// Bad: passes even when createUser is broken, because nothing is checked
test('creates a user', async () => { await createUser('ada@example.com'); });

// Good: fails when the user is not stored
test('creates a user', async () => {
  await createUser('ada@example.com');
  expect(await findUser('ada@example.com')).toMatchObject({ email: 'ada@example.com' });
});

How to check

The linter reports no test without an assertion. Breaking the code under a new test turns it red.