Use a single npm target to run unit tests (GoogleChrome#1430)

* Combine test steps into one npm script.

* Update README

* Return the test run exit status as the overall exit status

Author: jrobbins

README.md

@@ -54,12 +54,10 @@ npm run lint
 To run unit tests:
 
 ```bash
-npm run start-emulator      # Start the emulator
-npm run test                # Reset the datastore emulator and start testing
-npm run stop-emulator       # Stop the emulator. You do not have to stop the emulator between consecutive tests
+npm test
 ```
 
-Note: featurelist is temporarily excluded because lit-analyzer throws `Maximum call stack size exceeded`.
+This will start a local datastore emulator, run unit tests, and then shut down the emulator.
 
 There are some developing information in developer-documentation.md.
 
@@ -70,7 +68,6 @@ There are some developing information in developer-documentation.md.
 
 - When installing the GAE SDK, make sure to get the version for python 2.7.  It is no longer the default version.
 
-- When running `npm start` you may get an ImportError for jinja2.tests.  This was caused by an over-general line in skip_files.yaml.  Pulling the latest source code should resolve the problem.
 
 #### Blink components
 

package.json

@@ -10,9 +10,10 @@
     "deps": "python -m pip install -t lib -r requirements.txt --upgrade",
     "travis-deps": "pip install -t lib -r requirements.travis.txt --upgrade",
     "dev-deps": "python -m pip install --no-deps -r requirements.dev.txt",
-    "test": "curl -X POST 'http://localhost:15606/reset' && python -m unittest discover -p '*_test.py'  -b",
+    "do-tests": "curl -X POST 'http://localhost:15606/reset' && python -m unittest discover -p '*_test.py'  -b",
     "start-emulator" : "gcloud beta emulators datastore start --host-port=:15606 --no-store-on-disk --consistency=1.0",
     "stop-emulator" : "curl -X POST 'http://localhost:15606/shutdown'",
+    "test": "(npm run start-emulator > /dev/null 2>&1 &); sleep 3; curl --retry 4 http://localhost:15606/ --retry-connrefused; npm run do-tests; status=$?; npm run stop-emulator; exit $status",
     "coverage": "python -m pip install --no-deps -r requirements.dev.txt && python -m coverage erase && python -m coverage run -m unittest discover -p '*_test.py' -b && python -m coverage html",
     "lint": "gulp lint-fix && lit-analyzer \"static/elements/chromedash-!(featurelist)*.js\"",
     "build": "gulp",