A few months ago I was visiting a client who was having a lot of problems using TDD.“It takes over half an hour to run our unit tests,” he said.“You are not doing TDD,” I said. “In order for tests to be valuable all of them must run fast—within a few seconds, or developers will stop running tests frequently.”“But how to I make them run fast?” he asked, “Just connecting to the database takes 30 seconds”So I showed him a technique called Dependency Injections that allowed him to insert a mock object instead of the database. â€...