Robert Basic has written up a new tutorial for the unit testers out there showing how to do some complex argument matching in Mockery, a popular testing tool that offers an alternative to PHPUnit's own mocking functionality.

This past weekend I did some issue maintenance and bug triage on Mockery. One thing I noticed going through all these issues, is that people were surprised when learning about the Mockery::on() argument matcher. I know Mockery’s documentation isn’t the best documentation out there, but this still is a documented feature.

He starts with a simple mock example, mocking out AClass and defining two method criteria (one with a once and another with a never). He points out that things are not always that simple and sometime more complex argument matching is required. The Mockery:on handler allows you to pass in a closure and do more complex evaluation of the values passed in. He includes an example of this, evaluating the result of a set of arguments passed in and ensuring they're all set.