Test-driven Development

In test-driven development, we first write a failing test, represented in many testing tools by the color red. We then implement code to get the test to pass, represented by the color green. Finally, if necessary, we refactor the code, changing its form (by eliminatingduplication, for example) without changing its function. This cycle is known as ‘‘Red, Green, Refactor.’’

We’ll begin by adding some content to the Home page using test-driven development, including a top-level heading (<h1>) with the content Sample App. The first step is to generate an integration test (request spec) for our static pages:

This creates the static_pages_spec.rb in the spec/requests directory. As with most generated code, the result is not pretty, so let’s open static_pages_spec.rb with a text editor and replace it with the contents of Listing 3.9.