Testing and debugging language Virtual Machines (VMs) is a laborious task without the proper tooling. This complexity is aggravated when the VM targets multiple architectures. To solve this problem, simulation-based VM generator frameworks allow one to write test cases on the simulation, but those test cases do not ensure the correctness of the generated artifact due to the semantic gaps between the simulated VM and generated VMs. We propose Test Transmutation to extend simulation-based VM generator frameworks to support test case generation. It validates the generated VM by also running test cases generated from existing simulation test cases. Results of the generated test cases are compared against the simulation test cases using differential testing. Moreover, test cases are automatically mutated with non-semanticpreserving mutations. Test Transmutation detects bugs that are representative of typical VM modifications. We demonstrate its effectiveness by applying it to a set of real test cases of the Pharo VM. It allowed us to find several issues that were unknown to the VM development team. Our approach shows promising results to test simulationbased VM generator frameworks.