Real life example

FrontEndDeveloper.test.ts

import { FrontEndDeveloper } from "./FrontEndDeveloper";
import { StackOverflow } from "./StackOverflow";

describe("FrontEndDeveloper tests", () => {
    it("should still drink coffee", () => {
        const webDeveloper = new FrontEndDeveloper(); 
        expect(webDeveloper.drinkCoffee()).toContain("coffee ☕");
    });

    it("should pretend to code", () => {
        const webDeveloper = new FrontEndDeveloper(); 
        expect(webDeveloper.code()).toContain("'How to write unit tests' (w/o jQuery)");
    });

    it("should have used StackOverflow while coding", () => {
        const stackOverflowSearchSpy = jest.spyOn(StackOverflow, "search");
        const webDeveloper = new FrontEndDeveloper(); 
        expect(webDeveloper.code()).toContain("'How to write unit tests' (w/o jQuery)");
        expect(stackOverflowSearchSpy).toBeCalledWith(expect.stringContaining("unit tests"));
    });
});