Loïc Faugeron continues his "Mars Rover" series of posts today with the latest in the series covering the "Locating" handler, the functionality responsible for handling requests for the rover's location.

In this series we're building the software of a Mars Rover, according to the following specifications. It allows us to practice the followings: Monolithic Repositories (MonoRepo), Command / Query Responsibility Segregation (CQRS), Event Sourcing (ES) and Test Driven Development (TDD)

We've already developed the first use case about landing the rover on mars, and the second one about driving it. We're now developing the last one, requesting its location

He makes use of the command bus pattern to create the handling for the module, doing validation in the Command object and a Bus to handle the command and perform its task. He starts, as usual, with the phpspec tests defining a class that can use a "find latest location" type instance and a "find" method to abstract out the location repsonse.