Hi, This was originally reported as a BabyMock bug but it looks like it effects normal test cases as well. Let's say I have a test like this: MyTest>>initialize super initialize. s := OrderedCollection new. "note that this is initialized here not in the setUp as we normally do" MyTest>>testWhatever s add: 42. 1 / 0. Open the Test Runner tool, run the test, it'll fail as expected. Now click on the failed test (in the test runner window) and the debugger will popup saying that #add: was sent to nil. Instance variables are cleared out after a test run but initialize is not called before running it again. Is this expected? The same doesn't cause any problems when I run it from the System Browser. -- Sent from: http://forum.world.st/Pharo-Smalltalk-Developers-f1294837.html