Add unit tests for NearbyMetrics.

Change-Id: Id40b0d3be43e4e84df7c359962bd60097d5ebc6c
diff --git a/nearby/tests/unit/AndroidManifest.xml b/nearby/tests/unit/AndroidManifest.xml
index c756ff2..86ce01b 100644
--- a/nearby/tests/unit/AndroidManifest.xml
+++ b/nearby/tests/unit/AndroidManifest.xml
@@ -21,7 +21,7 @@
     <uses-permission android:name="android.permission.INTERNET"/>
     <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
 
-    <application>
+    <application android:debuggable="true">
         <uses-library android:name="android.test.runner" />
     </application>