reader: add Android test script

Change-Id: Ie23bf05f7e875a24878963e8a5e2962abc6e47c7
diff --git a/Makefile b/Makefile
index 64f75fa..45c6e34 100644
--- a/Makefile
+++ b/Makefile
@@ -1,5 +1,6 @@
 MAKEFLAGS += --warn-undefined-variables
 SHELL := /bin/bash
+GRADLE := android/gradlew
 
 .SHELLFLAGS := -eu -o pipefail -c
 .DEFAULT_GOAL := all
@@ -8,13 +9,18 @@
 .PHONY:
 clean:
 	$(MAKE) -C web clean
+	$(GRADLE) -p android clean
 
 .PHONY:
-test:
+test: test-android
 	$(MAKE) -C web test
 
+.PHONY:
+test-android:
+	$(GRADLE) -p android :app:test
+
 .PHONY: vdl
 vdl:
 	$(MAKE) -C web vdl
-	gradle -p android vdl
+	$(GRADLE) -p android vdl