Jest

All Jest’s functions, such as describe, it, expect etc., are already required when you run jest command, so in the test suite there’s no need to import anything.

Example of a test:

// test/Appointment.test.js
describe("Appointment", () => {
  it("renders the customer first name", () => {
    expect(document.body.textContent).toContain("Ashley");
  });
});

toContain() is a matcher function.