Don't let the fact that you have to use SOAP deter you from writing tests, here's you can mock SoapClient
So you want to start using Test Driven Development, but you're mired in a past that paid no attention to tests or testability; you aren't alone!
Behavioral Driven Development frameworks like Behat and Mink have a very specific set of language that they use, you can use this style of language to keep your tests focused and organized.
When it comes to using Selenium, you have options. In this post I'm going to talk through using the PHPUnit_Extensions_Selenium2TestCase.