I recently finished Effective Software Testing – A Developer’s Guide by Maurício Aniche, and I really liked it. I have been coding for a long time and I think I have been writing pretty good tests for the features I have implemented. Even so, I found this book quite valuable. Particularly the chapters on how to systematically come up with test cases based on the specification, inputs, outputs and the structure of the implementation.
Choosing test values when writing unit tests is mostly guided by the need to cover all cases of the program logic. However, some values are better than others. Here are a few tips on how to pick values that make mistakes easy to spot and the tests easy to read. Plus a bonus tip on a quick way to double check your tests.
For the past few years, I have heard many people advocating using only automatic tests. For example, if all the automatic tests pass, then the code should automatically be deployed to production. I have always performed a bit of manual testing before feeling confident about my code. So for the past year I have paid extra attention to bugs I have found manually testing my own code. My conclusion: manual testing is still needed. Continue reading
I recently found out about the book Developer Testing – Building Quality Into Software by Alexander Tarlinder, and I immediately wanted to read it. Even though I am a developer at heart, I have always been interested in software testing (I even worked as a tester for two years).
I think the subject of the book, developer testing, is timely. There seems to be a broad trend where more and more responsibility for testing is given to developers. It follows from the move towards micro services, dev ops and the “you built it, you run it” principle. Another driving force is the prevalence of developer testing frameworks that started with JUnit and now includes many more. These frameworks encourage and help developers write automatic tests.
Despite this trend of increasing developer testing, my feeling is that many developers still don’t test their programs well enough. For example, they may test the “happy path”, but not the different error handling cases. That is why I was excited about this new book explicitly addressing developer testing. Continue reading
A few months ago I came across the article Why Most Unit Testing is Waste by James O Coplien. The title is an accurate description of the contents – James considers most unit tests to be useless. He expands his arguments in the follow-up article. I was quite intrigued, since I get a lot of value from unit tests. How come we have such different views of them? Had I missed something? As it turns out, I was not persuaded by his arguments, and here is my response to the articles. Continue reading
When I first heard about unit testing using a framework like JUnit, I thought it was such a simple and powerful concept. Instead of ad hoc testing, you save your tests, and they can be run as often as you like. In my mind, the concept didn’t leave much room for misunderstanding. However, over the years I have seen several ways of using unit tests that I think are more or less wrong. Here are 5, in order of importance:
How can you unit test private methods? If you google this question, you find several different suggestions: test them indirectly, extract them into their own class and make them public there, or use reflection to test them. All these solutions have flaws. My preference is to simply remove the private modifier and make the method package private. Why is this a good idea? I will get to that after I discus the problems with the other methods. Continue reading