Android Studio Espresso 2.0 ClassNotFoundException

File this under “I’m writing this so when I Google for it in 6 months, it pops up”. 

I recently set up an existing Android project with Espresso 2.0 and immediately stared running into this error when I ran the tests: 

Running tests
Test running started
Test running failed: Instrumentation run failed due to 'java.lang.ClassNotFoundException'
Empty test suite.

I spent some time last night fighting this error and then I figured out the solution this morning.

The problem is that I’m using Dagger in this project and Espresso 2.0 also uses Dagger (see Espresso Dependencies). The core problem is that the ‘javax.inject’ dependency was borking the test run. 

How to to Fix

Change this

androidTestCompile('com.android.support.test.espresso:espresso-core:2.0')

to this: 

androidTestCompile('com.android.support.test.espresso:espresso-core:2.0') {
   exclude group: 'javax.inject'
}

Problem solved.