CODEWITHSUNDEEP
unit-testing
Luca Fülbier
Luca Fülbier

Reputation: 2731

DRY while writing tests

When writing tests i usually have some methods creating test data:

@Test
public void someMethod_somePrecondition_someResult() {
    ClassUnderTest cut = new ClassUnderTest();
    NeededData data = createNeededData();
    cut.performSomeActionWithTheData(data);

    assertTrue(cut.someMethod());
}

private NeededData createNeededData() {
    NeededData data = new NeededData();
    // Initialize data with needed values for the tests
    return data;
}

I think this is a good approach to minimize duplication in the test class (most unit testing frameworks also provide functionality to set up test data). But what if i test classes that need similar test data? Is it a good choice to provide every test class with its own createNeededData() method, even if they are all the same, or should i use other classes to generate test data to minimize code duplication?

Upvotes: 0

Views: 76

Answers (1)

Daniel Figueroa
Daniel Figueroa

Reputation: 10666

Disclaimer: I haven't used what I'm suggesting here yet, so this is just what I believe.

I recently read about a pattern called object mother which basically is a factory that creates objects with the different data that you might need. M. Fowler also talks about these objects as akin to personas, that is, you might generate different objects that represents different use cases.

Now the object mother pattern is not without it's problems, it can easily grow a lot and become quite cumbersome to maintain as your project grows. In this article 'TEST DATA BUILDERS AND OBJECT MOTHER: ANOTHER LOOK' the author talkes about using the builder pattern to create testobjects, which he concludes is also not perfect and then goes on to hypothesize about a combination between a builder combined with an object mother.

So basically you'd use the object mother pattern to bootstrap some repetetive data, and then use the returned builder to configure the object to your tests specific

I believe that wether you should do it like explained above or just repeat yourself in your tests (which isn't necessarily a bad thing when it comes to testing) is a matter of trying to evaluate the cost of implementing this contra continuing with how you're doing things now.

Upvotes: 1

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