'test' functions as an adjective. 'result' functions as a noun. The subject is 'My test result' or 'My test results'. The verb is 'is' for singular nouns and 'are' for plural nouns.
1. My test result is pretty good. :D (One result)
2. My test results are pretty good. :D (More than one result/test)
3. My tests results are pretty good. :(
4. My tests result are pretty good. :(
All the best, :D