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

As for my case, defining a function parameter was the problem.

@Test
fun foo(string: String = "") {  // Causes "Delegate runner could not be loaded" error.
    // ...
}

I had to do something like the following.

@Test
fun foo() {
    foo("")
}

fun foo(string: String) {  // Can be called from other test functions.
    // ...
}