Assert(Result.ToString() == "Expected")

I'm writing some C++ code at the moment, after months of C#. I'm trying to be very Test First, writing Red tests, then making them turn Green.

I'm also using CppUnit for the first time. It's not as easy as NUnit. You can't just declare your test method with an attribute, you have to declare the test method in a header file, place it inside a macro, and then have the test implementation in a .cpp file. And there's no nunit-gui. I'm using a post-build step to run the tests, which makes it fairly pain free.

There was one internal method that I didn't have an explicit test for, although I had tests for methods that called it. The main obstacle was that I didn't have a simple way to check the result, as the method returned a vector of objects. I didn't want to have to construct another vector of expected results.

Then it came to me: I could wrap the vector in a class and write a ToString() method for it (as well as a ToString() for the contained objects), and compare that to a string constant: 

 RateList result = creative.GetRates();
 CPPUNIT_ASSERT(result.ToString() == "100_4x3:100_16x9|200_16x9|400_4x3:400_16x9");

In retrospect, it should have been obvious. I already have ToString() methods for many of my other objects, and I'm using CPPUNIT_ASSERT(actual.ToString() == expected) in many of my unit tests. The extra step of writing ToString() for the collection blocked my thinking.

2 Comments

  • Just a question George, if your business entities are in C++ but .NET then could you write your tests in C# with NUnit but call your entities from the C++ assemblies? Might make writing the tests easier.

  • This is a standalone C++ library which is called from an ISAPI filter, and at this point it's finished. The rest of the codebase is C#. If I expected to do more work in C++ for this product, what you suggest would be worth experimenting with.

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