Add CTS test for public sdk extension properties am: 895c44793c am: 846c8e02fa

Original change: https://android-review.googlesource.com/c/platform/packages/modules/SdkExtensions/+/1515622

Change-Id: I44bb9c0012d051faa6cb8e4485e7de22ada7dd27
diff --git a/tests/cts/src/android/os/ext/cts/SdkExtensionsTest.java b/tests/cts/src/android/os/ext/cts/SdkExtensionsTest.java
index 884f5ef..a320a84 100644
--- a/tests/cts/src/android/os/ext/cts/SdkExtensionsTest.java
+++ b/tests/cts/src/android/os/ext/cts/SdkExtensionsTest.java
@@ -17,6 +17,7 @@
 package android.os.ext.cts;
 
 import android.os.Build;
+import android.os.SystemProperties;
 import android.os.ext.SdkExtensions;
 import junit.framework.TestCase;
 
@@ -40,4 +41,9 @@
             assertEquals(0, SdkExtensions.getExtensionVersion(sdk));
         }
     }
+
+    /** Verifies that the public sysprops are set as expected */
+    public void testSystemProperties() throws Exception {
+        assertEquals("0", SystemProperties.get("build.version.extensions.r"));
+    }
 }