Add unit tests for Rect

Bug: 161793589
Test: atest Rect_test
Change-Id: I0a43cff94b5794fbc65d5c16d693f0f6fe35374d
diff --git a/libs/ui/tests/TEST_MAPPING b/libs/ui/tests/TEST_MAPPING
index 7fcd7de..eece18e 100644
--- a/libs/ui/tests/TEST_MAPPING
+++ b/libs/ui/tests/TEST_MAPPING
@@ -2,6 +2,9 @@
   "presubmit": [
     {
       "name": "Size_test"
+    },
+    {
+      "name": "Rect_test"
     }
   ]
 }