title: Test android app writen in java with kotlin test
body: <p>I'm trying to add UI-tests to my android app, decided to work with kotlin and not with Java.
  I have added a new kotlin file to my "androidTest" folder 
  I followed <a href="https://developer.android.com/training/testing/ui-testing/espresso-testing.html#setup" rel="nofollow noreferrer">this tutrial</a>
  When I'm trying to run the test i'm getting: </p>
  
  <pre><code>Empty test suite.
  </code></pre>
  
  <p>just to emphasize - I'm writing to test in kotlin but the app is written in Java, is that even ok? or it can't even work? </p>
  
  <p>My code: </p>
  
  <pre><code>package maakesher.com.black.packagename
  import android.support.test.espresso.Espresso.onView
  import android.support.test.espresso.action.ViewActions.click
  import android.support.test.espresso.matcher.ViewMatchers.withId
  import android.support.test.rule.ActivityTestRule
  import androidx.test.filters.LargeTest
  import org.junit.Before
  import org.junit.Rule
  import org.junit.Test
  
  @LargeTest
  class ChangeTextBehaviorTest {
  
      private lateinit var stringToBetyped: String
  
      @get:Rule
      var activityRule: ActivityTestRule&lt;MainMenuActivity&gt; = ActivityTestRule(MainMenuActivity::class.java)
  
      @Before
      fun initValidString() {
          // Specify a valid string.
          stringToBetyped = "Espresso"
      }
  
      @Test
      fun testSomeStuff() {
          // Type text and then press the button.
          onView(withId(R.id.start_button))
                  .perform(click())
      }
  }
  </code></pre>
  
  <p>Thanks. </p>