Update README.md with testing against test tenancy

README.md

@@ -80,6 +80,24 @@ $ cd /path/to/this/repo
 $ pip3 install -e .
 ```
 
+## Testing against gdev.apps.cam.ac.uk, (UCam test Google Workspace)
+
+Install as above, and also clone the [sync-deploy](https://gitlab.developers.cam.ac.uk/uis/devops/gsuite/sync-deploy/)
+repo in a sibling folder called `sync-deploy`.
+
+Download the gsuite-sync-test GCP service account [JSON credentials file](https://start.1password.com/open/i?a=D3ATZUD36RDHLDKSVJUQZWGORQ&h=uis-devops.1password.eu&i=2lbuuuuwlttak4oevbdet6isua&v=uedkwk4hqb3dr2svf4xvmthtpy)
+from 1password and save as `credentials.json`.
+
+Take the API keys from [Directory Sync Tool App](https://developer.api.apps.cam.ac.uk/my-apps/aef2e7a3-1d2e-4d65-8029-6210b683f67b)
+in API Gateway and create `api_gateway_credentials.json`, as described in "Preparing API Gateway credentials"
+below.
+
+The tool can then be run against the test Google Workspace using the configuration file
+from the `sync-deploy` repo. e.g. the following to dry-run sync just users not groups:
+```
+$ gsuitesync --configuration ../sync-deploy/test.yaml --just-users
+```
+
 ## New users
 
 When new users are created they are created with a random password which is