Nsryjdtyk

Make sure your app in debug build variant. Go to Build > Select Build Variant... and the following should show up:

I made the mistake to put the test classes at src/test. After moving them to src/androidTest/java/ the dependency was resolved.

Ok so here is your mistake and mine!

If we are going to write a pice of code for Local Unit Testing we shouldn't use @RunWith(AndroidJUnit4.class) cause we do not use AndroidJUnit4 but we need Junit4. so we should write @RunWith(JUnit4.class). And of course your java test file is under app/src/test/java/your.package.name directory.

Else if (!!) we want to write some Android Instrumented Unit Test we should put our test java files in app/src/androidTest/java/your.package.name directory and use annotation like @RunWith(AndroidJUnit4.class)

I solved the problem by making a small change in the app's build.gradle file. In the dependencies { ... } section, make sure to include the following line:

debugImplementation 'com.android.support.test:runner:1.0.1'

or whatever version is the newest at that point (...Compile is deprecated and has been replaced by ...Implementation). Note the use of debugImplementation. Android Studio suggested auto-including it with androidTestImplementation, which didn't work.

I found out how to change it from test to debug by looking in Project Structure under Dependencies of the app module, where you can change the scope of each dependency, see below.

In my case this helped for release variant:

android {

    ...

    testBuildType "release" 

}

put this code in your Dependencies

compile fileTree(dir: 'libs', include: ['*.jar'])

androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {

    exclude group: 'com.android.support', module: 'support-annotations'

})

If anyone still having this issue:

Cannot resolve symbol 'AndroidJUnit4'

and using API 27, in the build.gradle which is in the app module, add the following lines:

testImplementation 'junit:junit:4.12'



// AndroidJUnitRunner and JUnit Rules

androidTestImplementation 'com.android.support.test:runner:1.0.2'

androidTestImplementation 'com.android.support.test:rules:1.0.2'



// Espresso dependencies

androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'

Adding

compile com.android.support.test:runner:0.5'

resolved this exact issue for me.

As the list of answers demonstrate, this can be caused by a few things. One more for the list:

I ran an over-zealous LINT which removed all unused imports. This will produce the same errors, and it is easy to miss that this is the problem.

Android-studio will highlight references that are missing in the test code - and the ALT-ENTER popup will appear (this is the bit that is easy to miss).

Next, I need to remove the tests from LINT - or at least disable this warning.

Edit: @Code-Apprentice, the lines that were missing were:

import org.junit.After;

import org.junit.Before;

import org.junit.Rule;

import org.junit.Test;

import org.junit.runner.RunWith;





import static junit.framework.Assert.assertNotNull;

import static junit.framework.Assert.assertNull;

import static org.junit.Assert.assertEquals;

import static org.junit.Assert.assertTrue;

So the first error in the file was with @RunWith(AndroidJUnit4.class) at the beginning of my test class.