An execution engine synchronizes test suite execution to run multiple independent operations concurrently or in parallel. The execution engine operates by stepping through the test suite. At each step it runs the required number of independent operations and waits for their completion. It then checks the results, and continues to the next step of the test suite. If at any step, the actual results are different from the expected results, then the exact sequence that triggered the fault is known. The sequence can be repeated when a correction is provided for the fault. Furthermore, the execution engine allows the user to interactively step through a test case when debugging a fault. A synchronization pattern generator may be incorporated in the system to generate minimal numbers of repetitions of test cases to guarantee varying degrees of interaction coverage.