assert is the testing library included with Brat. It works by setting up a series of tests, which include one or more assertions. Then it runs all the tests and collects the results. Each test is given a name so it can be reported when a test fails.
The basic usage looks like this:
The output from running the code above looks like this:
Loading tests... Running tests... (1/1) addition Test failure(s): 1. 'addition': expected 5, but was 4 1 tests, 1 assertions, 1 failures.