Merge "docs: Noted that test purchases have empty order ID." into mnc-docs

docs/html/google/play/billing/billing_reference.jd

@@ -228,7 +228,9 @@ a purchase order.</p>
   <tr>
     <td>{@code orderId}</td>
     <td>A unique order identifier for the transaction. This identifier
-      corresponds to the Google payments order ID.</td>
+      corresponds to the Google payments order ID. If the order is a test
+      purchase made through the In-app Billing Sandbox, {@code orderId} is
+      blank.</td>
   </tr>
   <tr>
     <td>{@code packageName}</td>

docs/html/google/play/billing/billing_testing.jd

@@ -82,9 +82,11 @@ accounts.</p>
 <p>Once authorized for testing access, those users can make purchases without
 being charged.
 Test purchases are real orders and Google Play processes them in the same way as
-other orders. When purchases are complete, Google Play prevents the orders from
+other orders. However, the <code>orderId</code> field for test purchases is
+blank.
+When purchases are complete, Google Play prevents the orders from
 going to financial processing, ensuring that there are no actual charges to user
-accounts, and automatically canceling the completed orders after 14 days. </p>
+accounts, and automatically canceling the completed orders after 14 days.</p>
 
 <p class="note">
   <strong>Note:</strong> Test subscription purchases recur daily, regardless of