I tried testing my app using Firebase Test Lab, but it is failing in every case.
This is the error it is showing:-
java.lang.RuntimeException: Unable to instantiate application android.support.multidex.MultiDexApplication: java.lang.ClassNotFoundException: Didn't find class "android.support.multidex.MultiDexApplication" on path: DexPathList[[zip file "/data/app/com.example.raman.snu_exams2-7QBxxpTz9mvJu3y7zUtBQw==/base.apk"],nativeLibraryDirectories=[/data/app/com.example.raman.snu_exams2-7QBxxpTz9mvJu3y7zUtBQw==/lib/x86, /system/lib, /system/vendor/lib]]
I tried installing the multidex dependency but it is still failing all the tests.
That error can occur if you're trying to test a debug APK that you built with Android Studio during development. During development, Gradle may create incremental builds that aren't complete APKs, in order to speed up compilation. This helps you deploy your app faster for local testing.
For testing on Test Lab, you'll need to build one full APK and upload that. You can create a whole new, complete APK on the command line with something like this:
./gradlew clean assembleDebug