Fastest way to create a mock Activity for testing

With androidX libraries, you can use ActivityScenario. Simply import androidTestImplementation("androidx.test:core:1.2.0") in your app.gradle file

Then, in your instrumented test, import ActivityScenario and launch the activity with:

import androidx.test.core.app.ActivityScenario

@Test
fun testActivity() {
    ActivityScenario.launch(MainActivity::class.java).onActivity { activity ->
        // do something with your activity instance
    }
}

Solved! Here's what I did:

• In the test project, I removed the target package in the instrumentation tab and added it again pointing to the test project base package, where the mock activity is.
• Added the target library as an Android Library in my test project. (Right click over test project -> properties -> Android -> Library -> added the target library).
• Added the mock activity in the test project manifest.

• To solve the exception I posted above, just replaced the test case constructor with this one:

      public LibraryTest() {
          super(MockActivity.class);
      }
  

Now that works and I can successfully launch dialogs. But in my brief research I stumbled upon Robotium. This library is just amazing. It is not needed for what I was trying to do at first, but I found it very useful to test GUIs in an automated way. Now I have a fresh new activity recreated in each setUp call.