Now that we have cookbooks that are adhering to the best practices of both Ruby and Chef, it is time to turn our attention away from static analysis and toward runtime testing. This is where we begin to move from a model of cookbooks-as-code to one of cookbooks-as-artifacts. Unit testing is a kind of middle ground, where we are doing a combination of code testing and artifact testing. This is also the point at which we move into a test-driven development model, where you write the tests before you write the code.

Ruby is a dynamically typed language. Ruby code is not type checked until it is executed. So in order to actually test our cookbooks, they have to be run. Before ChefSpec, this meant that you had to make the code changes to your cookbooks on your workstation, upload your modified cookbooks to your Chef server, then finally converge a node that is assigned that cookbook in order to be able to actually test your changes. This was a work- and time-intensive...