Noel Rappin Writes Here

Speed matters. But not precisely. There are only two things that matter when thinking about the speed of your automated tests: How fast can you run the relevant set of tests to let the tests be helpful in development? How fast can you run a complete, green build for deploy? We’re talking about the first one in this essay. In development, you want to be able to run the tests you are writing and a subset of tests that are most likely to break based on your changes.