What are fixtures? Why are they needed?

Fixtures are pre-prepared data or states used for testing. They allow creating a predictable and controlled environment so that tests are stable and reproducible.

Why fixtures are needed:

• They provide consistent conditions for each test run.
• They help isolate the tested functionality from external dependencies.
• They speed up the testing process by avoiding the need to manually create data.

Example of a fixture in JavaScript tests using Jest:

const userFixture = {
  id: 1,
  name: 'Ivan',
  email: 'ivan@example.com'
};

test('check user name', () => {
  expect(userFixture.name).toBe('Ivan');
});