Add "Testing done" section to PR template (#7218)

.github/PULL_REQUEST_TEMPLATE.md

@@ -14,6 +14,18 @@ If the issue is not fully described in Jira, add more information here (justific
  * Major new features should have a Jira issue.
 -->
 
+### Testing done
+
+<!-- Comment:
+Provide a clear description of how this change was tested.
+At minimum this should include proof that a computer has executed the changed lines.
+Ideally this should include an automated test or an explanation as to why this change has no tests.
+Note that automated test coverage is less than complete, so a successful PR build does not necessarily imply that a computer has executed the changed lines.
+If automated test coverage does not exist for the lines you are changing, you must describe the scenario(s) in which you manually tested the change.
+For frontend changes, include screenshots of the relevant page(s) before and after the change.
+For refactoring and code cleanup changes, exercise the code before and after the change and verify the behavior remains the same.
+-->
+
 ### Proposed changelog entries
 
 - Entry 1: Issue, human-readable text