Expand checklist usds#2 to cover test coverage

...so you can actually answer key question usds#1

_plays/10.md

@@ -7,7 +7,7 @@ Today, developers write automated scripts that can verify thousands of scenarios
 
 #### checklist
 1. Create automated tests that verify all user-facing functionality
-2. Create unit and integration tests to verify modules and components
+2. Create unit and integration tests to verify modules and components and verify test coverage
 3. Run tests automatically as part of the build process
 4. Perform deployments automatically with deployment scripts, continuous delivery services, or similar techniques
 5. Conduct load and performance tests at regular intervals, including before public launch