Well, hundreds of lines of mock structs is probably a sign that there is something very fundamentally wrong with the code. Go, as a language, has nothing to do with it. Testing is one of its nicest features. I only had to improve my testing experience just a bit, like stringifying complex outputs to compare them easily, comparing all of outputs with expected outputs in a single if statement and issuing a single verbose t.Errorf on failure, showing what functions produced what outputs on what inputs and what was expected.