Improve diagnostics when cannot install wellbeing test apk

This apk is used for Wellbeing tests.

Test: local
Bug: 187761685
Change-Id: I66f7c308b70b6bd048806d6417417a6e398605db
diff --git a/tests/src/com/android/launcher3/util/TestUtil.java b/tests/src/com/android/launcher3/util/TestUtil.java
index 55e5744..67f3902 100644
--- a/tests/src/com/android/launcher3/util/TestUtil.java
+++ b/tests/src/com/android/launcher3/util/TestUtil.java
@@ -22,6 +22,8 @@
 
 import androidx.test.uiautomator.UiDevice;
 
+import org.junit.Assert;
+
 import java.io.FileOutputStream;
 import java.io.IOException;
 import java.io.InputStream;
@@ -48,7 +50,10 @@
         in.close();
         out.close();
 
-        UiDevice.getInstance(getInstrumentation()).executeShellCommand("pm install " + apkFilename);
+        final String result = UiDevice.getInstance(getInstrumentation())
+                .executeShellCommand("pm install " + apkFilename);
+        Assert.assertTrue("Failed to install wellbeing test apk; make sure the device is rooted",
+                "Success".equals(result.replaceAll("\\s+", "")));
     }
 
     public static void uninstallDummyApp() throws IOException {