A physical computer system includes a processor and a memory configured to store instructions executable by the processor to implement a virtualization module, which in turn implements virtual machine(s) as a service on behalf of clients. Each virtual machine executes an operating system that is distinct from any underlying operating system executed by the physical computer system. The virtualization module instructs that the virtual machine(s) perform a computation that has been identified as a repeatable computation, to generate an original terminal state of the repeatable computation. In response to a request to repeat the repeatable computation, the virtualization module instructs that the virtual machine(s) perform the repeatable computation to generate a new terminal state of the repeatable computation, and, dependent upon a comparison of the original and new terminal states, to determine whether the repeatable computation has been successfully repeated according to a success criterion.