add Nudge debugging tips (#11158)

docs/Contributing/Testing-and-local-development.md

@@ -38,6 +38,7 @@
     - [Testing MDM](#testing-mdm)
       - [Testing manual enrollment](#testing-manual-enrollment)
       - [Testing DEP enrollment](#testing-dep-enrollment)
+    - [Nudge](#nudge)
 
 ## License key
 
@@ -602,4 +603,34 @@ Reference the [Apple DEP Profile documentation](https://developer.apple.com/docu
 
 3. Boot the machine, it should automatically enroll into MDM.
 
+### Nudge
+
+We use [Nudge](https://github.com/macadmins/nudge) to enforce macOS updates. Our integration is tightly managed by Orbit:
+
+1. When Orbit pings the server for a config (every 30 seconds,) we send the corresponding Nudge configuration for the host. Orbit then saves this config at `<ORBIT_ROOT_DIR>/nudge-config.json`
+2. If Orbit gets a Nudge config, it downloads Nudge from TUF.
+3. Periodically, Orbit runs `open` to start Nudge, this is a direct replacement of Nudge's [LaunchAgent](https://github.com/macadmins/nudge/wiki#scheduling-nudge-to-run).
+
+#### Debugging tips
+
+- Orbit launches Nudge using the following command, you can try and run the command yourself to see if you spot anything suspicious:
+
+```
+open /opt/orbit/bin/nudge/macos/stable/Nudge.app --args -json-url file:///opt/orbit/nudge-config.json
+```
+
+- Make sure that the `fleet-osquery.pkg` package you build to install `fleetd` has the `--debug` flag, there are many Nudge logs at the debug level.
+
+- Nudge has a great [guide](https://github.com/macadmins/nudge/wiki/Logging) to stream/parse their logs, the TL;DR version is that you probably want a terminal running:
+
+```
+log stream --predicate 'subsystem == "com.github.macadmins.Nudge"' --info --style json --debug
+```
+
+- Nudge has a couple of flags that you can provide to see what config values are actually being used. You can try launching Nudge with `-print-json-config` or `-print-profile-config` like this:
+
+```
+open /opt/orbit/bin/nudge/macos/stable/Nudge.app --args -json-url file:///opt/orbit/nudge-config.json -print-json-config
+```
+
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