I would like to have some feedback on http://code.google.com/p/pharo/issues/detail?id=1392 Issue 1392: Adapted SUnit TestRunner can not be integrated easily in environment I've build some extension on SUnit: http://www.squeaksource.com/SUnitsSlowNFast/ . It automagically can run fast and slow tests (based on yesterdays weather). However if i want to integrate this testrunner instead of the standard testrunner, there is no way 2 do it without changing existing code. I want something that i can configure my testrunner instead of the default one. If i look at the StandardToolSet>>class>>openTestRunner Smalltalk at: #TestRunner ifPresent: [ :class | ^ class open ]. You notice that TestRunner is hardcoded chosen. My suggestion is to adapt the same solution as in the StandardToolSet>>class>>openClassBrowser SystemBrowser default open message: another layer of indirection solves every problem and introduce a TestRunnerBrowser class, which is a subclass of AppRegistry, and there the default TestRunner is configured (which should be initialized in TestRunner>>class>>initialize using self). So that if i load my new TestRunner (which is a subclass of the TestRunner class) included in my SUnitsSlowNFast package, mine is automagically configured in the environment as the default one. In attachments i've created a solution.