phpspec is a package which allows us to use Behavior-Driven Development, BDD, which comes from Test-Driven Development, TDD. When applying BDD, we write our tests first and then only enough code to pass our tests and then refactor and verify the tests still pass exactly as we would with TDD. This cycle continues and is often referred to as red-green development of writing tests that fail and enough code to make them pass, then restarting the process.