Run all UI/Unit tests from multi-module Android project using a single command

We have a multi-module Android project, in which some modules contain UI tests and some contain Unit tests. We wish to run all UI tests from all modules using a single Gradle command and do the same thing for Unit tests.

The only way that we found to do this was with the following config inside the main app module that implements all the other sub-modules (basically make the app module know about all the other androidTest and test folders in the project):

app/build.gradle:

 sourceSets {
        androidTest.java.srcDirs += ["${project(':feature-login').projectDir}/src/androidTest/java"]
        test.java.srcDirs += ["${project(':feature-login').projectDir}/src/test/java"]
        test.java.srcDirs += ["${project(':core').projectDir}/src/test/java"]
    }

Then we run the following Gradle commands:

./gradlew app:connectedDemoDebugAndroidTest
./gradlew app:testDemoDebugUnitTest

Question: Is there a better/simpler way to achieve this? Or is there a way to add the androidTest and test folders from the above solution dynamically (using a relative path), instead of having to write the srcDirs line for each and every module (we have 40+ modules)?