Hi doyz,
I understand your problem with using runtests() to run the test script that you have written. I can safely assume with your code snippet that you are working with class based unit tests in MATLAB. There is a specific way to write class based unit tests for it to be registered as tests in MATLAB. Refer to the following page and the example given in the page that talks in detail about class based unit tests in MATLAB.
Thanks and Regards,
Viggnesh Venkatakrishnan