I finally figured out how to do this this week. This problem has been
nagging me for two years.
Sooner or later, when you build a Ruby testing framework of a certain
degree of complexity, it seems to stop counting your assertions. So
when you run the tests, you are incorrectly told you have no
assertions. This is really annoying and makes you look like an idiot.
What kind of tester doesn’t put any verification in his tests? When
things are still working, it looks like this:
Finished in 10.285 seconds.
6 tests, 8 assertions, 0 failures, 0 errors
But then you get 0 assertions, even though you know your assertions are
actually being executed. Why? (And if you look closely, you’ll see they
do get counted when they fail!)
The problem typically comes when you put assertions in your library
modules. This isn’t hard. All you have to do is put include
Test::Unit::Assertions in your module or helper class and then you can
include calls to assert, assert_equal and all the other assert methods.
It works, except that your assertions aren’t counted.
The reason why is that the method add_assertion does the counting. This
is automatically called by all the assert methods. When they call the
add_assertion method of TestCase, the count shows up in your test
results no problem. But the add_assertion method of the Assertions
module is just a no op. This is why they don’t affect the assertion
count. The solution is to add a functional add_assertion method back to
your helper module/class that ties back to your test case.
Here’s how. The first thing is to keep track of the test case that is
running. We’ll just put it in a global variable, which is ugly, but it
works. The best place to put this is in the setup method of your test
$testcase = self
The test case is actually the object the setup method is part of, so
self gives us a reference to it when it runs. You may already have
other stuff in your setup method as well. That’s fine; just add this
Now we need to make a change to your helper class/module where you did
the include Test::Unit::Assertions. Add this method:
The name for what we are doing here is “delegation,” except that we are
doing it in a totally non-object-oriented way. We are “delegating” the
call to add_assertion back to the test case where it belongs. After
you’ve made these changes, tell your developer friends that you fixed
the assertion count problem by delegating the call to add_assertion
back to the test case. They’ll be impressed.
But don’t start bragging yet. If you run your code right now, you’ll
get a complaint that you are calling a private method. I’ve seen some
clever hacks to get around this problem, but actually Ruby makes the
solution really easy. Just make the method public! Add this code to
your TestCase class definition:
Try doing that in Java! Don’t put in any of the methods; just put it
inside the class definition. To recap, your test case should now look
something like this:
class MyTest < Test::Unit::TestCase
$testcase = self
# other stuff maybe
# your actual tests…