docs: added some notes on how to run tests

docs/dev_notes.md

@@ -5,7 +5,7 @@ We set this up so it is hosted as a huggingface space. Each commit to `main` tri
 For local testing, assuming you have all the required packages installed in a
 conda env or virtualenv, and that env is activated:
 
-```
+```bash
 cd src
 streamlit run main.py
 ```
@@ -17,15 +17,17 @@ We have a CI action to presesnt the docs on github.io.
 To validate locally, you need the deps listed in `requirements.txt` installed. 
 
 Run
-```
+```bash
 mkdocs serve
 ```
+
 And navigate to the wish server running locally, by default: http://127.0.0.1:8888/
 
 This automatically watches for changes in the markdown files, but if you edit the 
 something else like the docstrings in py files, triggering a rebuild in another terminal
 refreshes the site, without having to quit and restart the server.
-```
+
+```bash
 mkdocs build -c
 ```
 
@@ -37,4 +39,44 @@ mkdocs build -c
 
 # Set up a conda env
 
-(Standard stuff)
+(Standard stuff)
+
+
+# Testing
+
+## local testing
+To run the tests locally, we have the standard dependencies of the project, plus the test runner dependencies. 
+
+```bash
+pip install -r tests/requirements.txt
+```
+
+(If we migrate to using toml config, the test reqs could be consolidated into an optional section)
+
+
+**Running tests**
+from the project root, simply run:
+
+```bash
+pytest
+# or pick a specific test file to run
+pytest tests/test_whale_viewer.py
+```
+
+To generate a coverage report to screen (also run the tests):
+```bash
+pytest --cov=src 
+```
+
+To generate reports on pass rate and coverage, to files:
+```bash
+pytest --junit-xml=test-results.xml
+pytest --cov-report=lcov --cov=src
+```
+
+
+## CI testing
+
+Initially we have an action setup that runs all tests in the `tests` directory, within the `test/tests` branch.
+
+TODO: Add some test report & coverage badges to the README.