diff --git a/android-interop-testing/app/build.gradle b/android-interop-testing/app/build.gradle
index 03d76c4ba1..26b2bf3d5b 100644
--- a/android-interop-testing/app/build.gradle
+++ b/android-interop-testing/app/build.gradle
@@ -76,6 +76,8 @@ dependencies {
     implementation 'io.grpc:grpc-protobuf-lite:1.21.0-SNAPSHOT' // CURRENT_GRPC_VERSION
     implementation 'io.grpc:grpc-stub:1.21.0-SNAPSHOT' // CURRENT_GRPC_VERSION
     implementation 'io.grpc:grpc-testing:1.21.0-SNAPSHOT' // CURRENT_GRPC_VERSION
+    
+    implementation 'org.mockito:mockito-core:2.25.1'
 
     // workaround for https://github.com/google/protobuf/issues/1889
     protobuf 'com.google.protobuf:protobuf-java:3.0.2'