How to build a release test apk for Android with Gradle?

I know, with the Gradle command assembleAndroidTest I can build a test APK. But I can use this test APK only for debug builds of my app, right? If I use it with a release build, I get error messages like "[SDR.handleImages] Unable to find test for com.xxx.xxx (packagename)"

How can I build a test APK in release mode with Gradle?