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30 Oct 2009
Ruby C Extensions Part 7: Testing

This is part 7 of the tale of my adventures in Ruby C extension land.

If you haven't read the other parts, you might want to go back there.

The Tower

As is inevitable in any good story, an evil wizard living in a tower has to occurr at some point.

That point is now.

It's a mean old wizard with a lizard on his shoulder wearing a monocle and a robe.

You better watch out, because he's going to curse you like he did to me.

The Testing Curse

So you wrote your C code and now you have to test it because the wizard forces you to.

No of course not.. You have of course written the tests in advance, haven't you? ;-)

Now, there are two ways to test your C code:

  1. Test it using Ruby
  2. Test it in C

Ruby Tests

These are the simple ones. Just wrap your functions and data structures in Ruby objects and write your unit tests, voila!

But you don't want to expose any of your internal structs and functions to normal Ruby code? Well, so did I. So I invented a little helper to work around that.

C Tests

Testing your C functions in C is pretty easy, once you've installed the rake-tester. It will take care of compilation and execution of your C tests while still leaving you the choice of the testing framework (e.g. cmockery).

To set it up, change your Rakefile as follows:

require 'rake/extensiontask'
require 'rake/extensiontesttask''cranberry', $gemspec) do |ext|
    # ...normal options...
    ext.test_files = FileList['test/c/*']

Just point test_files to all the C files that contain your tests.

Rake-tester will automatically link them against your native code and compile them with debugging symbols.

Now you can execute

rake test:c

to re-compile and start all your tests.

Additional Features

Furthermore, rake-tester offers gdb and valgrind integration:

rake test:gdb:cranberry[test]
rake test:valgrind:cranberry[test]

Just replace test with the test you want to execute. For example, if you have a file called test_allocation.c then you can start valgrind on that test suite with

rake test:valgrind:cranberry[test_allocation]

This made my life much easier. I hope it helps you as well.

Now go and write good tests for your C code and get rid of all those memory leaks.

I'll think hard about the next part, which might already be the last one about C extensions...

Continue with Part 8!