given:
        runner.tasksToRun = ['build']
        runner.warmUpRuns = 39
        runner.runs = 40

        def changedFile = getFileToChange(changeType)
        def changeClosure = getChangeClosure(changeType)
        runner.addBuildMutator { invocationSettings ->
            new BuildMutator() {
                String originalContent
                File originalContentFor

                @Override