added unit test

Readme.md

@@ -65,6 +65,7 @@ Here's what the environment variables mean:
 * `CELLXGENE_DATA` - a directory that can contain subdirectories with `.h5ad` data files, *without* trailing slash, e.g. `/mnt/cellxgene_data`
 * `GATEWAY_HOST` - the hostname and port that the gateway will run on, typically `localhost:5005` if running locally
 * `GATEWAY_PROTOCOL` - typically http when running locally, can be https when deployed if the gateway is behind a load balancer or reverse proxy.
+* `GATEWAY_EXTRA_SCRIPTS` - (optional) JSON array of script paths, will be embedded into each page and forwarded with `--scripts` to cellxgene server
 
 The defaults should be fine if you set up a venv and cellxgene_data folder as above.
 
@@ -73,11 +74,11 @@ The defaults should be fine if you set up a venv and cellxgene_data folder as ab
 The current paradigm for customization is to modify files during a build or deployment phase:
 
 * To modify CSS or JS on particular gateway pages, overwrite or append to the templates
-* To add script tags such as for user analytics to all pages, overwrite the extra_scripts.py file.
+* To add script tags such as for user analytics to all pages, set GATEWAY_EXTRA_SCRIPTS
   * these scripts will also be run on the pages served by cellxgene server via the --scripts parameter
   * See https://github.com/chanzuckerberg/cellxgene/pull/680 for details on --scripts parameter
 
-Currently we use a build.sh that copies the gateway to a "build" directory before modifying with sed and the like.
+Currently we use a bash script that copies the gateway to a "build" directory before modifying templates with sed and the like. There is probably a better way.
 
 # Development
 
@@ -106,6 +107,12 @@ python setup.py develop
 
 For convenience, the code repo includes a `run.sh.example` shell script to run the gateway.
 
+## Running Tests
+
+```bash
+    python -m unittest discover tests
+```
+
 ## Running Linters
 
 pip install isort flake8 black