Add testing section to pull_request_template.md (#1341)

.github/pull_request_template.md

@@ -1,10 +1,19 @@
-Thanks for submitting a pull request. Please include the following information.
+_Thanks for submitting a pull request. Please include the following information._
 
 **What I have done and why**
-Include a summary of what your pull request contains, and why you have made these changes.
+
+_Include a summary of what your pull request contains, and why you have made these changes._
 
 Fixes #<issue_number_goes_here>
 
+**How I'm testing it**
+
+_Choose at least one:_
+- Unit tests
+- UI tests
+- Screenshot tests
+- N/A _(provide justification)_
+
 **Do tests pass?**
 - [ ] Run local tests on `DemoDebug` variant: `./gradlew testDemoDebug`
 - [ ] Check formatting: `./gradlew --init-script gradle/init.gradle.kts spotlessApply`