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(this post explains WHY I would want to do this: Good patterns for unit testing form beans that have annotation-based validation in Spring MVC)

Is it considered good practice to write a unit test to just test configuration/annotations on a field or a class? For example if you have:

@AnnotatedClass
public class MyClass {

@AnnotatedField1
@AnnotatedField2
private string myField;

}

Is there any point in writing a unit test that checks the presence of annotations above?

Community
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Ashkan Aryan
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3 Answers3

5

The basic answer is "Yes - it's fine to check for annotations in unit tests"

Always ask yourself "what am I testing". Unit tests test that the "code is correct" at a class/method level.

You are not really "testing" the code, but you are asserting that coders have correctly annotated certain fields, which in your case is part of asserting that "code is correct", so "yes" - I think it's acceptable to "test" this.

Another option is to make this assertion part of the code style checking phase of your build (if you're doing that) - you would have to write a custom code style to do it, but I feel that would be a more appropriate place to check this. However, that's probably a bit painful to set up, so just do it as a unit test.

Bohemian
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  • Thanks. The purpose of that test in this case would to to ensure that certain fields have correct validation constraints applied to them. In that sense I don't see any harm in these tests, especially if they're complimented by integration and automated acceptance testing. In other words, this simple unit test will just test that the bean is configured correctly, and subsequent integration/acceptance tests will check whether the combination of these behaves as expected within the framework/container etc. – Ashkan Aryan Mar 02 '12 at 10:55
  • I really see no reason why verifying the presence of annotations should be excluded from testing, especially if the absence of such annotations would result in a breakage of your app. Test away. – Cedric Beust Mar 02 '12 at 18:35
2

I would't say so but it's only my personal opinion. Presence of particular annotations and their correct usage can be tested within integration tests easily. Personally, I follow rule that within unit tests I cover only java code of a particular class. DB mappings, JSR annotations, GWT UiFields markers and so on are tested within integration tests.

omnomnom
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How are you going to write such a test? You'll read through your source code, and wherever you see this annotation, you'll write the appropriate test, right? So in every case, you'll be writing a test for a condition that you already know is true.

Spend your time developing more features instead. Seriously.

Dawood ibn Kareem
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  • Yes that's correct, and that's my main consideration AGAINST it. – Ashkan Aryan Mar 02 '12 at 10:53
  • I might not have been clear. The proposed unit test is a waste of time. – Dawood ibn Kareem Mar 02 '12 at 10:57
  • I gathered that, and that was my main line of thinking and reason for posting this. But are we saying that there's no benefit in (unit) testing whether a form is configured properly or not, and it should be all left to integration testing? – Ashkan Aryan Mar 02 '12 at 11:00
  • Perhaps you could get a second person to write the unit test, based on their understanding of the requirements? Don't know. But it seems that if you got it wrong when you wrote the class, you'll get it wrong when you write the test too. – Dawood ibn Kareem Mar 02 '12 at 11:03
  • 100% agree. It really wouldn't give you a huge amount in terms of TDD. It may be good for preventing regression though. – Ashkan Aryan Mar 02 '12 at 11:31
  • You use reflection for this, it's straightforward and since your app might break without the annotation, you should definitely make it part of your test suite. – Cedric Beust Mar 02 '12 at 18:35
  • Straightforward, maybe. Economic, no. When the benefit of adding a test is less than the cost, it's time to stop. – Dawood ibn Kareem Mar 02 '12 at 23:01