Against Unit Tests

When discussing the topic of unit testing and methodologies they might entail (mostly TDD, i.e. Test-Driven Development), I noticed a curious imbalance in the number and strength of arguments pro and contra. The latter are few and far between, up to the point of ridiculous scarcity when googling “arguments against TDD” is equally likely to yield stories from both sides of the fence. That’s pretty telling. Is it so that TDD in general and unit tests in particular are just the best thing ever, because there is an industry-wide consensus about them?…

I wouldn’t be so sure. All this unequivocal acknowledgement looks suspiciously similar to many other trends and fashions that were (or still are) sweeping through the IT domain, receding only when the alternative approach gains enough traction.

O RLY?

Take OOP, for example. Back in the 90s and around 2000, you would hear all kinds of praise for the object-oriented methodology: how natural it is, how it helps to model problems in intuitive way, how flexible and useful its abstractions are. Critics’ camp existed, of course, but they were small, scattered and not taken very seriously. Objects and classes were reigning supreme.

Compare this to present day, when OOP is taking blows from almost every direction. On one hand, it is rejected on performance basis, as the unknown factors of virtual method’s call are seen as a liability. On the other hand, its abstraction patterns are considered baroque, overblown and outdated, unfit for modern computing challenges – most notably concurrency and asynchronism.

Could it be that approaches emphasizing the utmost importance of unit tests are following the same route? Given the pretty much universal praise they are receiving, it’s not unimaginable. In this context, providing some reasonable counterarguments seems like a good thing: if we let some air out of this balloon, we may prevent it from popping later on.

Incidentally, this is a service for TDD/unit testing that I’m glad to provide ;-) So in the rest of this post, I’m going to discuss some of their potential drawbacks, hopefully helping to even-out the playing field. Ultimately, this should always lead to better software engineering practices, and better software.