Writing Your First Test
To test that this setup works the way we expect, let's write a simple class and a test for it.
If you've seen or written RSpec tests, this test should be fairly familiar. If not, the gist of what's happening is that we're requiring the application.js file from the asset pipeline, which by default includes our greeter.js.coffee file. It then sets up a test and asserts that the sayHello function behaves correctly.