Add developer guidelines (#769)

* Add developer guidelines

* minor formatting

* PR clarifications/lint

* more pr fixes

* link fix

* below->above

* pr suggestions

dev_docs/developer_guidelines.md

@@ -0,0 +1,91 @@
+# Developer guidelines
+
+### Requirements
+- npm
+- Python 3.6+
+- Chrome
+
+[See dev section of README](../README.md)
+
+**All instructions are expected to be run from the top level cellxgene directory unless otherwise specified.**
+
+## Server dev
+### Install
+* Build the client and put static files in place: `make build-for-server-dev`
+* Install from local files: `make install-dev`
+
+### Launch
+* `cellxgene launch [options] <datafile>`
+
+### Reloading
+If you install cellxgene using `make install-dev` the server will be restarted every time you make changes on the server code. If changes affects the client, the browser must be reloaded.
+
+### Linter
+We use `flake8` to lint code. Travis CI runs `flake8 server`.
+
+### Test
+1. Install development requirements `pip install -r server/requirements-dev.txt`
+2. Run tests `pytest server/test`
+
+### Tips
+* Install in a virtualenv
+* May need to rebuild/reinstall when you make client changes
+
+## Client dev
+### Install
+1. Install prereqs for client: `npm install --prefix client/ client`
+2. Install cellxgene server: `pip install -e .` Caveat: this will not build the production client package - you must use the [server install](#install) instructions above to serve web assets.
+
+### Launch
+To launch with hot reloading you need to launch the server and the client separately. Node's hot reloading starts the client on its own node server and auto-refreshes when changes are made.
+1. Launch server (the client relies on the REST API being available): `cellxgene launch [options] <datafile>`
+2. Launch client: in `client/` directory run `npm run start`
+3. Client will be served on localhost:3000
+
+### Build
+To build only the client: `make build-client`
+
+### Linter
+We use `eslint` to lint the code and `prettier` as our code formatter.
+
+### Test
+In `client/` directory run `npm run unit-test`
+
+### Tips
+* You can also install/launch the server side code from npm scrips (requires python3.6 with virtualenv) in `client/` directory run `npm run backend-dev`
+
+## Running tests
+Client and server tests run on Travis CI for every push, PR, and commit to master on github. End to end tests run nightly on master only. 
+
+### Server unit tests
+Install development requirements `pip install -r server/requirements-dev.txt`
+Run tests `pytest server/test`
+
+### Client unit tests
+In `client/` directory run `npm run unit-test`
+
+### End to end tests
+
+End to end tests use two env variables:
+* `JEST_ENV` - environment to run end to end tests. Default `dev`
+    * `prod` - run headless with no slowdown, chromium will not open.
+    * `dev` - opens chromimum, runs tests with minimal slowdown, close on exit.
+    * `debug` - opens chromium, runs tests with 100ms slowdown, dev tools open, chrome stays open on exit.
+* `JEST_CXG_PORT` - port that end to end tests are being run on. Default `3000` (client hosted port).
+
+On CI the end to end tests are run with `JEST_ENV` set to `prod` using the `smoke-test` npm script
+
+To run end to end tests as they will be run on CI
+1. cellxgene should be built and installed as [specified in server dev](#install)
+2. `export JEST_ENV='prod'`
+3. `export JEST_CXG_PORT='5000'`
+4. Run `npm run --prefix client/ smoke-test`
+
+Run end to end tests interactively during development
+1. cellxgene should be installed as [specified in client dev](#install-1)
+2. Follow [launch](#launch-1) instructions for client dev with dataset `example-dataset/pbmc3k`
+3. Run `npm run --prefix client/ e2e`
+4. To debug a failing test `export JEST_ENV='debug'` and re-run.
+
+
+