Required methods

new

Creates a new assertion object. Takes whatever arguments you desire. Isn't strictly necessary for the framework to work with this class but is generally considered a good idea.

do_assertion

This is the important one. If Test::Unit::Assert::assert is called with an object as its first argument then it does:

    $_[0]->do_assertion(@_[1 .. $#_]) ||
        $self->fail("Assertion failed");
    

This means that "do_assertion" should return true if the assertion succeeds and false if it doesn't. Or, you can fail by throwing a Test::Unit::Failure object, which will get caught further up the stack and used to produce a sensible error report. Generally it's good practice for do_assertion to die with a meaningful error on assertion failure rather than just returning false.