Prose\ExpectsFailure::when PHP Method

    public function when($what, $callback)
    {
        // what are we doing?
        $log = usingLog()->startAction("expect {$what} to fail");
        // let's do it
        try {
            $callback();
        } catch (E5xx_ProseException $e) {
            // do nothing
            $log->endAction("{$what} failed (this is the expected behaviour)");
            return;
        }
        // do not catch any other exceptions ... they are unexpected
        // failures
        // if we get here, then the action did not fail - and THAT
        // is a failure
        throw new E5xx_ExpectFailed(__METHOD__, "{$what} failed", "{$what} did not fail");
    }