Skorks, a great ruby/dev blog, gave the following challenge last year:

what is the minimum amount of code needed to make a viable unit testing framework?

An interesting question… Well, he chose to replicate rspec, and managed it in 44 lines of code. Not bad! I decided to try the same but instead of rspec, I’d try to create a minimal version of the granddaddy of them all: test::unit. Here are the tests that I’d use to write the test runner against:

And this is the kind of output I’d want the tests to produce:

So… how to make this work… in as little code as possible…

Test::unit works around the idea of test classes. Any method that begins with test_ that is defined in a class that inherits from Test::Unit::TestCase would get executed in the context of a new instance of the class. Instead of the long-winded class name from test::unit, my test class name is TinyTest. The only assertion I’m going to provide is assert which tests that its argument is true. If what’s passed is not true then TinyTest will raise an error saying which line of which file the failed assertion was on; its class and method would also be reported. I also want setup and teardown functionality.

Like Test::Unit, I don’t want to have to tell the tests to execute, I want that to happen by magic. So, all the execution logic would need to go in an at_exit block. I want a passing test to print a ‘.‘, and a failing test to print an ‘F‘. Just like Test::Unit does. Finally, at the end of executing all the tests, I want to know how many of them passed and how many failed; and for each failure I want to know the file name, the line number, the class name and the method where the failure occurred.

Here’s what I put together:

28 lines! Not bad!!! How’s about that, huh? OK, it’s no cucumber, rspec, minitest or even test::unit… but it works! It does the job of a super simple test runner! I guess I could squash it further by using semi-colons instead of new lines, but that would be cheating. 28 lines it is!