temp-user.spec.ts

describe('TempUserService', () => {
    it('when we call read without a temp user in there should read null', () => {
        // arrange
        const c = setup().build();
        // act
        const result = c.readEmail();
        // assert
        expect(result == null).toBe(true);
    });
});

function setup() {
    // the autospy       VVVVV    will create an object with the methods of the class mocked
    const localStorage = autoSpy(Storage);
    const builder = {
        localStorage,
        build() {
            return new TempUserService(localStorage);
        },
    };

    return builder;
}