Since this trait requires special command line arguments you should place it in a new file. Have a look at [test/runnable/traits_getUnitTests.d](https://github.com/D-Programming-Language/dmd/blob/master/test/runnable/traits_getUnitTests.d), especially [the first line](https://github.com/D-Programming-Language/dmd/blob/master/test/runnable/traits_getUnitTests.d#L1). In this file you can leave some assertions to validate the trait returns empty strings. In the new file, validate it returns the correct string.