building androidTest apk gets R8 errors: "already has a mapping"

Question

I have added minifyEnabled=true to my 'release' build. The app runs correctly. And the androidTest apk runs correctly (all tests pass).

If I add any of the following to proguard-rules.pro:

-keepattributes LineNumberTable
-keepattributes LocalVariableTable
-keepattributes LocalVariableTypeTable

the app apk will build without error, but while building the androidTest apk I get ~4000 R8 "already has a mapping" errors for task:

:app:transformClassesAndResourcesWithR8ForReleaseAndroidTest

The (truncated) error log is

It appears that the methods that are getting the error are in 3rd party libraries (included as dependencies).

Thanks in advance for any help.

Answer 1

I solved the problem by adding an additional buildType for testing the 'release' configuration ('releaseTest'). It inherits from 'release', and sets debuggable=true.

buildTypes {
    debug {
        ...
    }
    release {
        ...
        minifyEnabled true    // enable code shrinking & obfuscation
        shrinkResources true  // enable resource shrinking
        ...
    }
    releaseTest {
        // inherit from 'release' buildType
        initWith release
        // for dependencies that don't know what 'releaseTest' is
        matchingFallbacks = ['release']

        debuggable true
   }