Fixes driver warnings in unit tests.
Fixes driver warnings in unit tests.

cfraz89/RxSwift,shiratsu/RxSwift,KyoheiG3/RxSwift,cfraz89/RxSwift,kzaher/RxSwift,cfraz89/RxSwift,thanegill/RxSwift,kzaher/RxSwift,KyoheiG3/RxSwift,thanegill/RxSwift,tottakai/RxSwift,thanegill/RxSwift,hsoi/RxSwift,hsoi/RxSwift,tottakai/RxSwift,kzaher/RxSwift,thanegill/RxSwift,tottakai/RxSwift,ReactiveX/RxSwift,shiratsu/RxSwift,ReactiveX/RxSwift,KyoheiG3/RxSwift,hsoi/RxSwift,kzaher/RxSwift,ReactiveX/RxSwift,shiratsu/RxSwift,cfraz89/RxSwift,hsoi/RxSwift