Android tests depends on test classes on a library project

so my project has two modules:

• app
• library

In the addroidTest directory of the app, I have some classes that depends on classes located in the addroidTest directory of the library.

The structure is:

:library /src/main
            /androidTests

:app     /src/main
            /androidTests

They compile finely in Android Studio, but when I run the tests I get:

Error:(6, 32) error: cannot find symbol class XXXX Error:Execution failed for task [...]

Compilation failed; see the compiler error output for details.

[....]

Execution failed for task > ':app:compileProductionDebugAndroidTestJavaWithJavac'.

It seems that when gradle executes the task ':app:compileProductionDebugAndroidTestJavaWithJavac' it cannot find classes located in the test directory of the library.

Any idea how can I solve this?