What is a good way to unit test templated c++ methods/classes/functions?

Question

I'm looking for a good way to unit test my templated methods, classes, and functions in c++. I have a feeling that it is not enough to just test using with a single type, and it doesn't feel right to just duplicate the unit tests and replace the types.

To be more specific, I'm working on a Matrix class and using Boost's unit testing framework. The Matrix is to work with different types. It will mainly be used for basic types, but I would like it to support concrete types too.

Note, I doing this for learning purposes, which is why I'm not using a existing matrix implementation.

Answer 1

Boost test has a macro BOOST_AUTO_TEST_CASE_TEMPLATE that runs a test on a template for each type in a boost::mpl::list.

template<typename T>
T Add(T lh, T rh)
{
   return lh + rh;
}

typedef boost::mpl::list<int, float> test_types;

BOOST_AUTO_TEST_CASE_TEMPLATE(Add_1Plus2_Is3, T, test_types)
{
    T result = Add(T(1), T(2));
    BOOST_CHECK_EQUAL(T(3), result);
}

http://www.boost.org/doc/libs/1_48_0/libs/test/doc/html/utf/user-guide/test-organization/auto-test-case-template.html

Answer 2

I agree with josuegomes and VJovic. I think, one way to minimize duplication of code is to make a templated function with your unit test logic and then call this with the different type arguments. This way, you are able to place all of your Matrix unit testing logic one place, while calling the templated unit test function once per each desired type.

However, it might be overkill to do so. I think it depends on the amount of logic in your tests.