Robolectric 4 AndroidX NoClassDefFoundError MonitoringInstrumentation with IntelliJ 2018.3.4

Question

Problem

• after switching to androidX
• with a multi-module Android library
• using IntelliJ 2018.3.4 #IC-183.5429.30
• using Robolectric 4.1 with android gradle plugin 3.3.1

• when executing Robolectric tests, I receive:

  java.lang.NoClassDefFoundError: androidx/test/runner/MonitoringInstrumentation
  

No duplicate question:

I read the other topics which pop up when using google or stackoverflow search but they are about a more specific error which is worked-around via adding specific dependencies. In my case I was not able to determine which dependency to add.

Answer 1

I add dependencies to androidx.test:core for the build type under test.

In my case it was debug so in the build.gradle I add

debugImplementation 'androidx.test:core:1.2.0'

Answer 2

I read that no workaround should be required with Android Studio 3.3 and Robolectric 4.0.

• Use Android Studio 3.3.1+ with Robolectric 4.0+

This works for me.