Mock a function's return value using a Sinon stub

When mocking a JavaScript function during a unit test, it can be helpful to force a mock function to return a value of your choosing. This allows you to verify that functions you're testing will behave correctly for every possible use case.

Much like sinon.spy(), sinon.stub() creates a mock function that prevents a real function from running. But, unlike spy, it also allows you to declare what value you'd like the mock function to return.