Hi Eliot. I took a Pharo 1.1.1 image (which has included the changes to run Cog) and I run all the tests with the build r2219 And these are the results: 9768 run, 9698 passes, 53 expected failures, 15 failures, 2 errors, 0 unexpected passes Failures: FloatTest>>#testRaisedTo MCInitializationTest>>#testWorkingCopy FloatTest>>#testReciprocal ReleaseTest>>#testUndeclared FloatTest>>#testDivide MethodContextTest>>#testClosureRestart FloatTest>>#testCloseTo FloatTest>>#testHugeIntegerCloseTo FloatTest>>#testInfinityCloseTo WeakRegistryTest>>#testFinalization PCCByLiteralsTest>>#testSwitchPrimCallOffOn AllocationTest>>#testOneGigAllocation FloatTest>>#testNaNCompare FileStreamTest>>#testPositionPastEndIsAtEnd NumberTest>>#testRaisedToIntegerWithFloats Errors: MessageTallyTest>>#testSampling1 WeakSetInspectorTest>>#testSymbolTableM6812 I think that most of these problems were fixed in latest official SqueakVM. I guess they were integrated in VMMaker in versions later than the one you used for Cog. Maybe you can integrate them and create a new version? I am not a VM expert so please if you can help us with this tests it would be cool. Thanks Mariano