How to create test classes that can be used in both Android tests and unit tests?

Question

I often find myself duplicating the exact same set of test classes such as mocks or helpers for both Android tests /androidTest and unit tests /test when writing tests for an application module.

For example, I have some static functions that help me set up mocks quickly in /test/MockUtils.java However, I cannot reuse this helper class in any of my Android tests because they do not share the same class path - /androidTest vs /test.

I've thought of creating a new module that only contains test resources. However, this idea won't fly because the Android Gradle plugin refuses to depend on an app module.

project testCommon resolves to an APK archive which is not supported as a compilation dependency.

Is there any other way to create test classes that could be reused in both Android tests and unit tests?

Answer 1

NOTE: This is a theorized solution, one that I have not tried.

Step #1: Create a testSrc/ directory in your module for which you are trying to set up the shared testing code.

Step #2: Put the shared code in that directory (with appropriate subdirectories based on Java package).

Step #3: Add the following closure inside your android closure in your module's build.gradle file:

sourceSets {
    androidTest {
        java.srcDirs <<= 'testSrc'
    }

    test {
        java.srcDirs <<= 'testSrc'
    }
}

What this should do is tell Gradle for Android that testSrc is another source directory for Java code in the androidTest and test sourcesets.

Answer 2

Based on CommonsWare's solution and https://code.google.com/p/android/issues/detail?id=181391, the correct way to add an additional class path is to use the += or <<= operators.

sourceSets {
    androidTest {
        java.srcDirs <<= 'testSrc'
    }

    test {
        java.srcDirs += 'testSrc'
    }
}

Answer 3

The solution described in the blog below helped me.

http://blog.danlew.net/2015/11/02/sharing-code-between-unit-tests-and-instrumentation-tests-on-android/

I put my shared test code into src/sharedTest/java . Then I added the following code to build.gradle:

<pre>
android {  
  sourceSets {
    String sharedTestDir = 'src/sharedTest/java'
    test {
      java.srcDir sharedTestDir
    }
    androidTest {
      java.srcDir sharedTestDir
    }
  }
}
</pre>