add tests

.travis.yml

@@ -3,6 +3,8 @@
 # needs these two lines:
 sudo: required
 dist: trusty
+addons:
+  chrome: stable
 
 language: python
 python:

nbconvert/preprocessors/tests/files/single-pixel.ipynb

@@ -0,0 +1,110 @@
+{
+ "cells": [
+  {
+   "cell_type": "code",
+   "execution_count": 1,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "application/vnd.jupyter.widget-view+json": {
+       "model_id": "9aa0769fd66e42fcb83d86241d228062",
+       "version_major": 2,
+       "version_minor": 0
+      },
+      "text/plain": [
+       "Image(value=b'\\x89PNG\\r\\n\\x1a\\n\\x00\\x00\\x00\\rIHDR\\x00\\x00\\x00\\x01\\x00\\x00\\x00\\x01\\x08\\x06\\x00\\x00\\x00\\x1f\\x15\\…"
+      ]
+     },
+     "metadata": {},
+     "output_type": "display_data"
+    }
+   ],
+   "source": [
+    "# this generates a 1 pixel image with the rgba values (100, 200, 250, 255)\n",
+    "# generated with the code in the next cells (kept for debugging purposes)\n",
+    "import base64\n",
+    "import ipywidgets\n",
+    "image_data = base64.b64decode('iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAADUlEQVR4nGNIOfHrPwAG4AMmv//laQAAAABJRU5ErkJggg==')\n",
+    "ipywidgets.Image(value=image_data)"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 2,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "# try:\n",
+    "#     from io import BytesIO as StringIO\n",
+    "# except:\n",
+    "#     from cStringIO import StringIO\n",
+    "# import PIL.Image\n"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 3,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "# f = StringIO(image_data)\n",
+    "# image = PIL.Image.new('RGBA', (1,1))\n",
+    "# image.putpixel((0, 0), (100, 200, 250, 255))\n",
+    "# image.save(f, format='png')\n",
+    "# base64.b64encode(f.getvalue())"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 4,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "# base64.b64encode(f.getvalue())"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 5,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "# image = PIL.Image.open(f)\n",
+    "# pixel = image.getpixel((0, 0))\n",
+    "\n",
+    "# #assert pixel == (100, 200, 250)\n",
+    "\n",
+    "# pixel"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": []
+  }
+ ],
+ "metadata": {
+  "kernelspec": {
+   "display_name": "Python 3",
+   "language": "python",
+   "name": "python3"
+  },
+  "language_info": {
+   "codemirror_mode": {
+    "name": "ipython",
+    "version": 3
+   },
+   "file_extension": ".py",
+   "mimetype": "text/x-python",
+   "name": "python",
+   "nbconvert_exporter": "python",
+   "pygments_lexer": "ipython3",
+   "version": "3.6.4"
+  }
+ },
+ "nbformat": 4,
+ "nbformat_minor": 2
+}

nbconvert/preprocessors/tests/test_snapshot.py

@@ -0,0 +1,32 @@
+import os
+
+import nbformat
+from ..snapshot import SnapshotPreProcessor
+from ..execute import ExecutePreprocessor
+import PIL.Image
+try:
+    from io import BytesIO as StringIO
+except:
+    from cStringIO import StringIO
+import base64
+
+current_dir = os.path.dirname(__file__)
+
+def test_red_pixel():
+    execute_preprocessor = ExecutePreprocessor(enabled=True)
+
+    input_file = os.path.join(current_dir, 'files', 'single-pixel.ipynb')
+    spp = SnapshotPreProcessor(page_opener_class='headless')
+    nb = nbformat.read(input_file, 4)
+    resources = {}
+    nb, resources = execute_preprocessor.preprocess(nb, resources)
+    assert 'image/png' not in nb.cells[0].outputs[0].data
+    nb, resources = spp.preprocess(nb, resources)
+    assert 'image/png' in nb.cells[0].outputs[0].data
+    # we cannot be sure the browser encodes it the same way
+    # assert nb.cells[0].outputs[0].data['image/png'] == 'iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAADUlEQVR4nGNIOfHrPwAG4AMmv//laQAAAABJRU5ErkJggg=='
+    # instead, we read the magic pixel values
+    f = StringIO(base64.b64decode(nb.cells[0].outputs[0].data['image/png']))
+    image = PIL.Image.open(f)
+    pixel = image.getpixel((0, 0))
+    assert pixel == (100, 200, 250, 255)

setup.py

@@ -228,8 +228,9 @@ def run(self):
 jupyter_client_req = 'jupyter_client>=4.2'
 
 extra_requirements = {
-    'test': ['pytest', 'pytest-cov', 'ipykernel', 'jupyter_client>=4.2', 'ipywidgets>=7'],
+    'test': ['pytest', 'pytest-cov', 'ipykernel', 'jupyter_client>=4.2', 'ipywidgets>=7', 'PyChromeDevTools', 'pillow'],
     'serve': ['tornado>=4.0'],
+    'snapshot': ['PyChromeDevTools']
     'execute': [jupyter_client_req],
     'docs': ['sphinx>=1.5.1',
              'sphinx_rtd_theme',