Migrating Junit4 tests to androidx: What causes 'delegate runner could not be loaded'?

Question

I am migrating my app to androidx, I can\'t seem to get my unit tests working. I took example from Google\'s AndroidJunitRunnerSample, which has been updated to use the new

Answer 1

You also get the error message if you use a test rule in Kotlin and write it Java style

@Rule
var mainActivityActivityTestRule = ActivityTestRule(MainActivity::class.java)

You have to change @Rule to @get:Rule

@get:Rule
var mainActivityActivityTestRule = ActivityTestRule(MainActivity::class.java)