Mutation testing can indicate whether mutants of a software application, created by intentionally altering source code of the software application, are successfully “killed” by test cases executed against the mutants. Mutation testing can be performed via parallel threads by, within each parallel thread, modifying individual source code class files and recompiling the modified class files to generate and test mutants. Individual mutation test results produced within each of the parallel threads can be aggregated to generate an aggregated test result report that indicates overall testing metrics associated with the mutation testing across the parallel threads.