TDD does not refer only to unit testing, it also includes the integration tests. Indeed, as you say, the value of unit tests is greatly diminished without integ

TDD does not refer only to unit testing, it also includes the integration tests. Indeed, as you say, the value of unit tests is greatly diminished without integration tests. If you're working outside-in your workflow is - Create integration test/stories - For each step in integration test - Add unit tests to make it pass, starting at the view layer and working backwards. The level of unit testing required for each step depends on the complexity of the code. So what does unit testing get you over just performing integration tests? 2 things: 1) Documents and enforces expected behaviour for edge cases that you haven't written integration tests for - e.g. unusual error conditions 2) Isolates points of inflexion in your system - your stories/use cases will often rely on several components that have multiple logic paths. When you combine the branching logic from several components the combinatorial range of behaviour can be vast. By isolating units at the points of inflexion you are able to test a far smaller range of inputs/outputs so that you can achieve effective test coverage. You're quite correct that the units you tests are not necessarily aligned 1 to 1 with your classes. However, given that a well designed class will have a single responsibility this is often the case.