[ENH] Need to evaluate how to extend C API testing

[rlratzel]

From #1907 (comment) :

The C++ unit tests all use RAII constructs so that we don't leak resources and can run a series of tests within the same executable and see all of the failures in a single run of the test. Without RAII constructs we can leak resources (most important is GPU memory) and potentially introduce phantom failures later in the sequence of tests (e.g. tests that fail because they run out of memory, although they would succeed if the memory had been freed).

The C unit tests can't use RAII constructs. I think we need to explore the following ideas:

• How extensively do we want to test the C API?
• Do we want to be able to have multiple tests and see all of the failures?
• How much effort do we want to go to in avoiding resource leaks in the tests when tests fail?

Based on the answers to these questions we can take some of these test cases and identify what macros we want to create that will make the unit tests easy to develop, read and maintain while satisfying the need.