Reduction of pseudo-random test case generation overhead

Embodiments of the present invention are directed to a computer-implemented method for building and executing test cases. A non-limiting example of the computer-implemented method includes building, using a processor, a master test case instruction stream including a plurality of instructions including a replaceable instruction. The computer-implemented method builds, using the processor, a test case instruction stream derivative including the plurality of instructions including a replacement instruction in lieu of the replaceable instruction, and predicts, using the processor, a predicted result of executing the test case instruction stream derivative in a test case environment. The computer-implemented method executes, using the processor, the test case instruction stream derivative on the test case environment to generate an actual test case result and compares, using the processor, the actual test case result with the predicted result to determine proper operation of the test case environment.