Check Build.SERIAL for Non-telephony Devices

Change-Id: I4f701ed06a9e1df999782293b313a950bc7ddd39
diff --git a/tests/tests/telephony/src/android/telephony/cts/TelephonyManagerTest.java b/tests/tests/telephony/src/android/telephony/cts/TelephonyManagerTest.java
index ece6328..deed336 100644
--- a/tests/tests/telephony/src/android/telephony/cts/TelephonyManagerTest.java
+++ b/tests/tests/telephony/src/android/telephony/cts/TelephonyManagerTest.java
@@ -24,6 +24,7 @@
 import android.content.Context;
 import android.net.wifi.WifiInfo;
 import android.net.wifi.WifiManager;
+import android.os.Build;
 import android.os.Looper;
 import android.os.cts.TestThread;
 import android.telephony.CellLocation;
@@ -295,6 +296,7 @@
 
             case TelephonyManager.PHONE_TYPE_NONE:
                 assertNull(deviceId);
+                assertSerialNumber();
                 assertMacAddressReported();
                 break;
 
@@ -391,6 +393,15 @@
                 Pattern.matches(meidPattern, deviceId));
     }
 
+    private void assertSerialNumber() {
+        assertNotNull("Non-telephony devices must have a Build.SERIAL number.",
+                Build.SERIAL);
+        assertTrue("Hardware id must be no longer than 20 characters.",
+                Build.SERIAL.length() <= 20);
+        assertTrue("Hardware id must be alphanumeric.",
+                Pattern.matches("[0-9A-Za-z]+", Build.SERIAL));
+    }
+
     private void assertMacAddressReported() {
         String macAddress = getMacAddress();
         String macPattern = "([0-9a-fA-F]{2}:){5}[0-9a-fA-F]{2}";