update docs

Author: woodthom2

content/en/_index.md

@@ -80,6 +80,10 @@ blocks:
     url: http://github.com/harmonydata/harmony
   - text: Google Colab notebook
     url: https://colab.research.google.com/github/harmonydata/harmony/blob/main/Harmony_example_walkthrough.ipynb
+  - text: Windows installation video
+    url: https://www.youtube.com/watch?v=Okk8tUMDr6g
+  - text: Linux (Ubuntu) installation video
+    url: https://www.youtube.com/watch?v=enWh0-4I0Sg
   code: |
     ```vshell
     pip install harmonydata

content/en/developer-guide.md

@@ -4,7 +4,7 @@ title: Developer guide
 
 If you're a researcher and you found Harmony useful for your research, please [cite us](/ai-in-mental-health/bmc-psychiatry-paper/). If you encounter a problem, a bug, or a feature which you would like us to implement, please [raise an issue on Github](https://github.com/harmonydata/harmony) or [message us on Discord](https://discord.gg/harmonydata).
 
-# Git and GitHub workflow
+## Git and GitHub workflow
 
 The preferred workflow for contributing to Harmony’s repository is to fork the [main repository](https://github.com/harmonydata/harmony/) on GitHub, clone, and develop on a new branch.
 
@@ -19,6 +19,21 @@ We have four main repositories on Github under the `harmonydata` organisation:
 
 This contributor guide focuses on the Python library, but you could follow the same steps for the other repositories.
 
+## Testing what you've done
+
+After you've made a change, please run the unit tests in any part of the code base that your changes might have affected, either directly or indirectly, to see if anything is broken:
+
+* the Harmony module https://github.com/harmonydata/harmony/tree/main/tests
+
+*  the API  https://github.com/harmonydata/harmonyapi/tree/main/tests
+
+Please try and run the tool e.g. front end and back end to check if you can get the tool working still with your changes:
+
+* [Python on Windows installation video](https://www.youtube.com/watch?v=Okk8tUMDr6g) (only relevant if you were working on Python)
+* [Python on Linux (Ubuntu) installation video](https://www.youtube.com/watch?v=enWh0-4I0Sg) (only relevant if you were working on Python)
+* [R on Windows installation video](https://www.youtube.com/watch?v=hFqg6T_BqZc) (only relevant if you were working on R)
+
+
 ## Hackathons, coding challenges and events
 
 Please contribute to our [hackathons](/open-source-for-social-science/hackathon/) and [coding challenges](/doxa/) to help improve the tool.  We appreciate coming to give talks at events such as [Women In Data™️](/open-source-for-social-science/women-in-data/), [AI|DL](/psychology-ai-tool/aidl-meetup/), [MethodsCon Futures](/ai-in-mental-health/harmony-at-methodscon-futures/), [Pydata](/open-source-for-social-science/pydata-meetup/), [Lifecourse](/ai-in-mental-health/harmony-at-lifecourse-seminar/), and [AI Camp](/psychology-ai-tool/aicamp-meetup/). If you run a similar meetup or community group we are willing to come and talk.