update testing notes

Author: nerrad

docs/testing/releases/510.md

@@ -0,0 +1,23 @@
+## Testing notes and ZIP for release 5.1.0
+
+Zip file for testing: [woocommerce-gutenberg-products-block.zip](https://github.com/woocommerce/woocommerce-gutenberg-products-block/files/6452221/woocommerce-gutenberg-products-block.zip)
+
+## Feature plugin only
+
+### General smoke testing
+
+The following are related to various changes impacting existing flows, so smoke testing is needed to verify there are no regressions:
+
+- Place orders via the Checkout block and ensure the following:
+  - All payment methods included with the blocks work as expected for completing the order.
+  - Intentionally triggering payment errors for various payment methods surface the errors as expected and another payment method can be tried.
+  - Express payment methods (via Stripe) work as expected in both the Cart context and Checkout context.
+
+### Fixed bug with clearing email and phone fields when using separate billing address.
+
+Test both guest and logged in scenarios for the following:
+
+- On checkout, fill out email address, shipping fields, and phone number.
+- Uncheck "use shipping for billing" checkbox.
+- Verify email and phone fields still have their values.
+- Submit the order and make sure those values persist on the server with the order.

docs/testing/releases/README.md

@@ -30,3 +30,4 @@ Every release includes specific testing instructions for new features and bug fi
 -   [4.9.0](./490.md)
 -   [4.9.1](./491.md)
 -   [5.0.0](./500.md)
+-   [5.1.0](./510.md)