docs: Additional testing documentation (#8001)

* Additional testing documentation

* snmpsim is required for save-test-data.php already

* Update Test-Units.md

doc/Developing/os/Test-Units.md

@@ -19,6 +19,9 @@ default when running `./scripts/pre-commit.php`.
 the --hostname (-h) allows you to capture all data used to discover and poll a device already added to LibreNMS.  Make sure to
 re-run the script if you add additional support. Check the command-line help for more options.
 
+Generally, you will only need to capture data (-h) once.  After you have the data you need in the snmprec file, you can
+update the json using -o (and -v if using a variant) after that.
+
 ### OS Variants
 
 If test data already exists, but is for a different device/configuration then you should use the --variant (-v) option to
@@ -82,3 +85,25 @@ Hex encoded strings (4x) should be used for any strings that contain line return
 ## New discovery/poller modules
 
 New discovery or poller modules should define database capture parameters in `/tests/module_tables.yaml`.
+
+## Example workflow
+If the base os (<os>.snmprec) already contains test data for the module you are testing or that data conflicts with your new
+data, you must use a variant to store your test data (-v).
+
+### Add initial detection
+1. Add device to LibreNMS. It is generic and device_id = 42
+2. Run `./scripts/save-test-data.php -h 42 -m os`, initial snmprec will be created
+3. [Add initial detection](Initial-Detection.md) for `example-os`
+4. Run discovery to make sure it detects properly `./discovery.php -h 42`
+5. Add any additional os items like version, hardware, features, or serial.
+6. If there is additional snmp data required, run `./scripts/save-test-data.php -h 42 -m os` otherwise, run `./scripts/save-test-data.php -o example-os -m os`
+7. Review data. If you modified the snmprec (don't modify json manually) run `./scripts/save-test-data.php -o example-os -m os`
+8. Run `./scripts/pre-commit.php --db --snmpsim`
+9. If the tests succeed submit a pull request
+
+### Additional module support or test data
+1. Add code to support module or support already exists.
+2. `./scripts/save-test-data.php -h 42 -m <module>`, this will add more data to the snmprec file
+3. Review data. If you modified the snmprec (don't modify json manually) run `./scripts/save-test-data.php -o example-os -m <module>`
+4. Run `./scripts/pre-commit.php --db --snmpsim`
+5. If the tests succeed submit a pull request