Add local testing instructions

LOCAL_INSTALL.md

@@ -90,6 +90,72 @@ REM this batch file goes at the root of the chatgpt-clone directory (C:/chatgpt-
 
 If you update the chatgpt-clone project files, mannually redo the `npm ci` and `npm run build` steps
 
+## Locally test the app during development
+
+### Run the app
+
+#### Option 1: Run the app using Docker
+
+For reproducibility and ease of use, you can use
+the provided docker-compose file:
+
+1. Comment out the portion pointing at the already built image
+
+   ```yaml
+   image: chatgptclone/app:0.3.3
+   ```
+   
+2. Uncomment the portion pointing at the local source code
+
+   ```yaml
+   # image: node-api
+   # build:
+   #   context: .
+   #   target: node-api
+   ``` 
+
+3. Build your local source code for the `node-api` target
+
+   ```shell
+   docker build `
+     --target=node-api ` 
+     -t node-api `
+     .
+   ```
+
+4. Docker-compose up
+
+   ```shell
+   docker-compose up
+   ```
+
+#### Option 2: Run the app by installing on your machine
+
+1. Install the prerequisites on your machine. 
+   See [section above](#install-the-prerequisites-on-your-machine).
+
+2. Run the app on your machine. 
+   See [section above](#run-the-app).
+
+### Run the tests
+
+1. Install the global dependencies
+
+   ```shell
+   npm ci
+   npx playwright install --with-deps
+   ```
+
+2. Run tests
+
+   ```shell
+   npx playwright test
+   ```
+   
+If everything goes well, you should see a `passed` message.
+
+<img src="https://user-images.githubusercontent.com/22865959/235321489-9be48fd6-77d4-4e21-97ad-0254e140b934.png">
+
 # Shared
 
 To share within network or serve as a public server, set `HOST` to `0.0.0.0` in `.env` file.