Update README.md

README.md

@@ -8,3 +8,25 @@ A Suite of functional tests for Grails
 To change the Geb driver used to run the functional tests supply the geb.env system property.
 
     ./gradlew -Dgeb.env=chromeHeadless iT   
+
+### Usage
+To test a PR in grails/grails-core with grails-functional-tests before merging:
+1. Publish the PR branch to Maven Local:
+   Run this in grails/grails-core:
+```
+./gradlew pTML
+```
+2. Checkout the relevant branch (e.g. 7.0.x) in grails/grails-functional-tests
+3. Add `mavenLocal()` at the top of the repositories block in the root `build.gradle` of `grails/grails-functional-tests`.
+https://github.com/grails/grails-functional-tests/blob/2df395bf60d42c4d596837453dc717e8c3d638e4/build.gradle#L26-L35
+4. Run the Functional Tests:
+   In grails/grails-functional-tests, run:
+```
+./gradlew build
+```
+5. Check the Results:
+   Verify that the build completes successfully.
+```console
+BUILD SUCCESSFUL in 4m 20s
+139 actionable tasks: 124 executed, 15 up-to-date
+```