See tests as living documentation

Tests are often treated as write-once-never-look-at-again code (unless just maybe if there is a bug). That is a shame, because it wastes much of the potential value tests can provide. Good tests are helpful for understanding a piece of code, and making code easier to understand is important since code is harder to read than to write.

To help make code easier to understand, I suggest that you should start looking at your tests as a living documentation of your code. View them as something that your colleagues will look at to understand the code. See them as something that you will look at to understand the code (later).

Focus on communication and intent

Why? Well, obviously, because they hopefully help you understand the code quicker. But it goes deeper than that – I believe it helps you write better implementation code. The reasons is that it helps you focus on communication and intent, rather than technical details. Because after all, the most important audience of code is not computers, but humans. Computers understand any code that is correct, no matter how it is structured. The same cannot be said for humans. You turn computer-focused tests into human-focused documentation.

Behavior-Driven Development go with this theme to turn tests into a collaboration tool between software developers and business experts.

Seeing tests as stories is an idea I learned from Kent Beck, JUnit’s creator, who said:

Writing a test is really comes down to telling a story about the code. Having that mindset helps you work out many other problems during testing.

What documentation-focused tests look like

A few examples of how viewing tests as documentation can affect your test writing.

  • Your start using longer, more descriptive method names.
  • You name test methods not only after the method they are testing, but describes what to expect.
  • You use multiple test classes for the same implementation class, separating groups of related tests. (These groups are called “fixtures” and are how JUnit was designed and intended to be used.)
  • You start sorting test methods in a way that makes them easy to grasp.
  • You accept somewhat higher duplication in your tests because readability of tests is so important.
  • You avoid abstract super classes for test classes as they make individual test classes harder to read.
  • You write tests before implementation code to help you focus on the purpose of the code.
  • You realize that the tests needed to drive design in Test-Driven Development are not necessarily the tests needed to show the intent of the code.
  • You understand that deleting tests comes down to story telling – which tests are needed to tell the story about this code.
  • You don’t obsess over 100% test coverage since you get less in return for each test you add.

Caveat: Of course, there is also a technical or coverage aspect of unit testing, but in most cases it is of less importance. The primary audience of code is humans, not computers.

StoryTeller to the rescue

The Related Tests view that StoryTeller provides.

If you want some help with the mind shift, that is where StoryTeller comes in. It is an Eclipse plugin that uses your unit tests as living documentation.

It helps you by displaying relevant tests side-by-side with your code, and displaying test names as normal sentences rather than method names.

By always having relevant tests available, you can use the tests as a quick reference of the code. You also get reminded about the tests regularly, so you can see if they accurately describe the code. If not, it might be time to add, modify, or remove a few tests.

StoryTeller also uses normal sentences rather than method names. WhileCamelCaseIsVeryUseful, plain old text is just easier to read. Using normal sentences also helps you think of the tests as specification or documentation, not just methods.

If you use Eclipse, go ahead and give StoryTeller a spin. You just might like it!

2 thoughts on “See tests as living documentation

  1. any sample? i would appreciate it if you end your discussion how to start using it…after installing the StoryTeller eclipse plugin then what? would I just write my test method? I can do it without installing the plugin though,,,

  2. Thank you for your question, kurisu!

    After you’ve installed StoryTeller, the “Related Tests” view should be automatically added to the Java perspective. If you’re using another perspective, you can open the view under Window > Show view > Other > StoryTeller > Related Tests. When this view is visible, it will display the names of the tests which are related to the code you are currently viewing.

    As you say, you can write test methods just fine without StoryTeller. What it tries to do is help you understand the code you are viewing. At the same time it also give you an quick way to see which tests are affected by the code you’re viewing, and encourage you to name your tests better.

    I’ll keep in mind to add some more detailed “getting started” instructions in the future.

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