Android's R file in androidTest is not generating when applicationIdSuffix is used

Question

I've created an Android project from scratch, with package name com.example.myapplication

I've a strings.xml file in the main package (app module), with a String called yyy. I've another strings.xml file in the androidTest package, with a String called xxx.

I can use both strings without problem in a instrumented test, simply using the correct R file:

class ExampleInstrumentedTest {
    @Test
    fun useAppContext() {

        // Context of the app under test.
        val appContext = InstrumentationRegistry.getInstrumentation().targetContext

        val stringFromApp = appContext.getString(com.example.myapplication.R.string.yyy)
        val stringFromTest = appContext.getString(com.example.myapplication.test.R.string.xxx)

        assertEquals("com.example.myapplication", appContext.packageName)
    }
}

But, if I add an applicationIdSuffix in debug variant, then androidTest's R file is not generated correctly. It seems a bug on the system:

        debug {
            applicationIdSuffix '.imasuffix'
        }

        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
        }
    }

class ExampleInstrumentedTest {
    @Test
    fun useAppContext() {

        // Context of the app under test.
        val appContext = InstrumentationRegistry.getInstrumentation().targetContext

        val stringFromApp = appContext.getString(com.example.myapplication.R.string.yyy)
        val stringFromTest = appContext.getString(com.example.myapplication.test.R.string.xxx)
        val stringFromNewSuffix = appContext.getString(com.example.myapplication.imasuffix.test.R.string.xxx)

        assertEquals("com.example.myapplication", appContext.packageName)
    }
}

As you can see, Android Studio suggests me to use the com.example.myapplication.imasuffix.test.R file but is not working, even Rebuilding the project or invalidating caches.

I've seen a similar issue related with Roboelectric, but I'm using the standard AndroidJUnit4 tests.

Thanks.