Android Studio module that depends on another module's tests

Question

I'm trying to get the Gradle Java plugin to execute jUnit tests that exist in an Android project. My solution was to create a second module that applies the Java plugin, and set the test sourceSet to the app module's src/test directory.

test-module's build.gradle:

apply plugin: 'java'
...
dependencies {
    ...
    testCompile project(':app-module')
}
sourceSets {
    test {
        java.srcDirs += ["${appDir}/src/test/java"]
    }
}

This works fine from the command line, but Android Studio refuses to import a project that has source sets outside the submodule. It throws the error: Can't register given path of type 'TEST' because it's out of content root.

.
├── app-module
│   ├── build.gradle
│   └── src
│       ├── main
│       └── test
├── test-module
│   └── build.gradle
├── build.gradle
└── settings.gradle

I tried configuring this from the parent build.gradle, but that didn't change anything. I can add app-module as a testCompile project dependency in test-module, but that doesn't cause test-module to add app-module's tests.

Any ideas for getting test-module to run app-module's tests without provoking Android Studio's limitation about remote source sets?