Add docs for Jupyter NB test suite

plotly/tests/test_optional/test_jupyter/README.md

@@ -0,0 +1,106 @@
+# plotly.py Jupyter Notebook JS test suite
+
+To make sure that plotly.py works properly inside Jupyter Notebooks in both
+`plotly.plotly` and `plotly.offline`, we here run JavaScript tests in a browser.
+
+See PR [#545](https://github.com/plotly/plotly.py/pull/545) for example of what
+can go wrong in Jupyter Notebooks.
+
+
+## Running the tests
+
+Install JavaScript dependencies:
+
+```bash
+(plotly.py/plotly/tests/test_optional/test_jupyter) $ npm install
+```
+
+Run the tests:
+
+```bash
+(plotly.py/plotly/tests/test_optional/test_jupyter) $ nosetests
+
+# or from the repo root
+(plotly.py) $ nosetests plotly/tests/test_optional/test_jupyter
+```
+
+## Add a test case
+
+- Open up `jupyter notebook`.
+
+- Add a few code cells testing what you wish to test. No need to execute them!
+
+- Save the resulting `.ipynb` file in `fixtures/` (e.g. `my_test.ipynb`)
+
+- Add a JavaScript test file in `js_tests/` by first requiring the in-house
+  [`tape`](https://github.com/substack/tape) test wrapper found in `lib/tape-wrapper.js`. 
+
+For example,
+
+```js
+var test = require('../lib/tape-wrapper');
+
+test('should have one plotly.js graph', function(t) {
+    t.plan(1);
+
+    var nodes = document.querySelectorAll('.js-plotly-plot');
+    t.equal(nodes.length, 1);
+});
+```
+
+asserts that one plotly graph is present in the notebook. 
+
+At the moment, it is highly recommended that the js test file has the same name
+(minus the extension) as the `.ipynb` fixture (i.e. `my_test.js` in this
+example).
+
+- Add a test case in `test_jupyter.py`. If both the fixture and js test file
+have the same name, simply add:
+
+```py
+class MyTest(Common):
+    __test__ = True
+    name = 'my_test'
+```
+
+to `test_jupyter.py` and you're done :beers:
+
+
+## How does this work?
+
+The `Common` test class in `test_jupyter.py`:
+
+- Loads up a given `ipynb` fixture
+
+- Executes all code cells and converts it to HTML using the
+[`nbconvert`](https://nbconvert.readthedocs.io/en/latest/) and
+[`ipykernel`](http://ipython.readthedocs.io/en/stable/install/kernel_install.html)
+modules. 
+
+- Saves the resulting HTML file is saved in `fixtures/` but is git-ignored.
+
+Then, `Common` runs an `npm` command in the shell:
+
+```bash
+npm test -- <path-to-html-fixture> <path-to-js-test-file>
+```
+
+which runs a minimal server using `lib/server.js`. 
+
+In details, `lib/server.js`:
+
+-  bundles up the js test code into a single bundle using
+[`browserify`](https://github.com/substack/node-browserify)
+
+- stubs in a `<script>` tag to include the js test bundle in the fixture HTML 
+
+- starts a simple http server
+
+- launches Chrome at the HTML fixture URL
+
+- once the page is loaded, the js tests are run and results are logged in the
+terminal
+
+
+See PR [#540](https://github.com/plotly/plotly.py/pull/549) for the details on
+how this suite was first implemented.

plotly/tests/test_optional/test_jupyter/test_jupyter.py

@@ -12,10 +12,17 @@
 import subprocess
 
 PATH_ROOT = path.dirname(__file__)
+PATH_NODE_MODULES = path.join(PATH_ROOT, 'node_modules')
 PATH_FIXTURES = path.join(PATH_ROOT, 'fixtures')
 PATH_JS_TESTS = path.join(PATH_ROOT, 'js_tests')
 
 
+class PlotlyJupyterTestDeps(TestCase):
+
+    def test_node_modules(self):
+        self.assertTrue(path.isdir(PATH_NODE_MODULES))
+
+
 class Common(TestCase):
     __test__ = False
     name = None