Question

There are several places, where one has to convert one data object into another. For example incoming data from a webservice or a REST service into an object that is persistable.

Is there a way to unit test that all incoming data gets filled into the right places of the “outgoing” objects without copying the converter logic inside the test?

If the fields are all called the same, and one is feeling adventurous, reflections could do some work.. But I don’t feel like going down that path..

Acceptance tests won’t catch a bug if say a Person that has a name and a firstname gets converted into a Person where name == firstname due to some copy+paste mistake.

So right now I just skip testing object/model conversion and rather take a really good look at my converter.

Has anyone any idea on how to do this differently?

Answer 1

If you need to test that multiplication works, you should not replicate the multiplication logic. Define test data that you know are correct, and test that the multiplicaiton is ok.

assert( 4*5, 20 )

and not

   assert( 4*5, 4*5 )

Here the test data are 4, 5, 20, and test that logic that ties them is the multiplication. The same principle holds in your case. Define test data and test that convertion produces the right results.

(As you point out, making test themsleves generic with reflection, etc., defeats the purpose of testing.)