import getCurrentUserTimeSinceSignup from '../get-current-user-time-since-signup'; describe( 'getCurrentUserTimeSinceSignup()', () => { beforeAll( () => { // Time travel. jest .useFakeTimers() // Mock date => 2022-01-01T05:04:12+00:00. .setSystemTime( new Date( 1641013452000 ) ); } ); afterAll( () => { // Back to present. jest.useRealTimers(); } ); test( 'It should return the correct amount of days from the user signup date', () => { // Fake global state. const prevState = { currentUser: { user: { date: '2013-02-12T23:34:51+00:00', }, }, }; const howManyDays = getCurrentUserTimeSinceSignup( prevState ); // It should be 3244 days expect( howManyDays ).toEqual( 3244 ); } ); test( 'It should round down the date difference to nearest day', () => { // Fake global state. const prevState = { currentUser: { user: { date: '2022-01-01T03:04:12+00:00', }, }, }; const howManyDays = getCurrentUserTimeSinceSignup( prevState ); // It should be 0 (2 hours) expect( howManyDays ).toEqual( 0 ); } ); test( 'It should round up the date difference to nearest day', () => { // Fake global state. const prevState = { currentUser: { user: { date: '2021-12-31T10:04:12+00:00', }, }, }; const howManyDays = getCurrentUserTimeSinceSignup( prevState ); // It should be 1 (19 hours) expect( howManyDays ).toEqual( 1 ); } ); } );