No error still Android Studio says “no tests were found”

Question

I am trying to write an instrumentation test for my MainActivity. I followed the answers given here. Still Android Studio cannot find any tests. I have the class Application

Answer 1

not sure if the problem has been found. Running into similar but only if added assertTrue() it got the "Empty test suite.".

but replace with assertNotNull() the test is fine, still cannot use assertTrue though (not know why).

(I'm using kotlin and modify the Android studio generated default test in the AndroidTest folder, and the test is coded in kotlin's companion object, if this make any difference). Update: using assertTrue() outside the companion object is fine.