Writing Great Unit Tests

In the blog post Writing Great Unit Tests: Best and Worst Practices, Steve Sanderson talks about the best and worst practices when writing unit tests. He goes over the true purpose of unit tests (each examining a unit of your code separately and as a whole cohesively working together to provide value that is more complex and subtle than the sum of its independently tested parts, not for finding bugs), as well as the purpose of integration tests (automate the entire system to detect regressions). At the end of his post, he also gives several useful tips for writing great unit tests, such as making each test orthogonal, or independent, to all other tests.

The reason I chose to talk about this blog post is because I think it’s definitely something that’s commonly overlooked by developers. As Sanderson said at the beginning of his post, “Even if you’re a brilliant coder with decades of experience, your existing knowledge and habits won’t automatically lead you to write good unit tests.” For people looking to get into software development, I think it’s important to learn how to write great unit tests early on so as to avoid having to clean up a self-inflicted mess in the future.

I found it interesting when he described the difference between unit tests and integration tests, as well as the problems that bad unit tests can cause. This image found in his post is useful for visualizing this:


The last section in which he gives practical advise for writing great unit tests is also something that I think will be useful in the future, although I think the formatting may have been messed up.

One thing that I have a hard time not necessarily agreeing with but understanding is how he said that unit testing isn’t for finding bugs. I think that, for example, if you were to make a change to the way a function performs its task (perhaps to optimize the code) while not trying to affect the end result, one of your unit tests failing because of this could be classified as “finding a bug.”

Source: http://blog.stevensanderson.com/2009/08/24/writing-great-unit-tests-best-and-worst-practises/

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