I'm plannig to tackle this case https://pharo.fogbugz.com/f/cases/7256/TestRunner-should-not-deal-with-UI I am all in for decoupling the TestRunner UI from the functionality it provides. And even making a new object that both the CommandLineTestRunner and the TestRunner use. I wouldn't do that subclassifying both from a common superclass. That is, I would use composition, not inheritance. Before I begin with this, anyone have some insight or thoughts to share?