Unit test product with license file

Question

Ive started working on a product that uses license files. These files need to be read (and verified) in order for the application to work. This causes some problems in the unit tests, without the proper license it throws exceptions.

We are using NUnit and what I need to do is either:

• Copy the license file into the shadow copied directory before the test is run.
• Set the working directory to the original build output folder so that file names are still valid in the temporary test folder.

I know that file access should generally be avoided in unit tests but before the refactoring can begin, we need the unit tests in place so I need this to work.

Answer 1

Not necessary an answer to your question, but usually when we buy a license for a software product it usually comes with some type of support. It might not be a bad Idea to just call and see if the vendor has a solution they would recommend.

Answer 2

I think you are aiming your test too far up the chain, you could write tests for the functions further down. One blanket test is not really a good way to do it, a start though I suppose. Try to balance the amount of time spent trying to get this test to work with how that time might be spent testing smaller more targetted units of work.

Answer 3

You need to write a mock class to replace the class that is reading the license file. You can use MOQ to achieve this.

Answer 4

I suggest you start with reading this book:

Working Effectively with Legacy Code

It will give you lots of insight into how to break open this type of problem. There will be some level of change to make such code testable that will have to happen without tests, but keep it as little as possible and do it very very carefully.

In your case, since injecting classes that fake reading licenses is too much of a jump, what you can do is change the class that validates the license file so that the actual validation logic is in a single method is launched from a single method that tells the rest of the class that the license is fine and make that method virtual, and then test with a subclass that overrides the method to pretend that it validated the file.

Then, once you have some tests around this class you can dump the method and subclass in favor of a properly injected class.

(Edited to respond to the fact that the validation is complex).

Answer 5

Disabling the Shadow Copy feature of NUnit will make the tests run in the same output folder as they were built in. But this will also block new builds (since the file is in use). A bad solution, imo, but a solution nontheless.