Working Effectively With Unit Tests is a discussion not of when to unit test or how to unit test, but how to know when you’ve done it well. It works backwards from the idea that tests should be Descriptive And Meaningful Phrases(DAMP) as opposed to the traditional software pneumonic Don’t Repeat Yourself (DRY). By allowing some duplication in tests and focusing on the clear intention of what is to be accomplished you get tests that are easier to read and tests that are more focused on the object under test rather than the collaborators of the test.
The style being described forces out a lot of the elaborate mock setups common in most first attempts at unit testing. This is a definite good intention, however like most resources, I feel it comes short at describing a means to actually get rid of these sorts of problems in real applications, as opposed to toy applications in books and articles. The ideas it provides do work towards those ends admirably. To me, the ideas presented seem to drive towards a more functional style of programming; methods were getting more arguments which made the methods more flexible, and the objects they lived on were less prone to carrying around extraneous state. The book didn’t discuss this in functional programming terms, but sort of implied that was a goal around the edges.
Compared to some of the other books on unit testing I’ve read, this felt more concise, and it was definitely less focused on a specific framework for doing testing. It feels written for someone who has been doing unit testing for a while and has not been getting value from the activity, or has been having maintainability problems with tests. For those audiences it seems like it is a good perspective towards trying to get out of their problems. For people new to unit testing, it may be a little to broad in what you should do and not prescriptive enough.