#!/usr/bin/env python
# coding: utf-8

# > This is one of the 100 recipes of the [IPython Cookbook](http://ipython-books.github.io/), the definitive guide to high-performance scientific computing and data science in Python.
# 

# # 2.7. Writing unit tests with nose
# 
# **This is the Python 3 version of the recipe.**
# 
# Although Python has a native unit testing module (unittest), we will rather use Nose which is more convenient and more powerful. Having an extra dependency is not a problem as the Nose package is only required to launch the test suite, and not to use the software itself.

# ## Creation of the Python module

# In[ ]:


get_ipython().run_cell_magic('writefile', 'datautils.py', '# Version 1.\nimport os\nfrom urllib.request import urlopen  # Python 2: use urllib2\n\ndef download(url):\n    """Download a file and save it in the current folder.\n    Return the name of the downloaded file."""\n    # Get the filename.\n    file = os.path.basename(url)\n    # Download the file unless it already exists.\n    if not os.path.exists(file):\n        with open(file, \'w\') as f:\n            f.write(urlopen(url).read())\n    return file\n')


# ## Creation of the test module

# In[ ]:


get_ipython().run_cell_magic('writefile', 'test_datautils.py', 'from urllib.request import (HTTPHandler, install_opener, \n                            build_opener, addinfourl)\nimport os\nimport shutil\nimport tempfile\nfrom io import StringIO  # Python 2: use StringIO\nfrom datautils import download\n\nTEST_FOLDER = tempfile.mkdtemp()\nORIGINAL_FOLDER = os.getcwd()\n\nclass TestHTTPHandler(HTTPHandler):\n    """Mock HTTP handler."""\n    def http_open(self, req):\n        resp = addinfourl(StringIO(\'test\'), \'\', req.get_full_url(), 200)\n        resp.msg = \'OK\'\n        return resp\n    \ndef setup():\n    """Install the mock HTTP handler for unit tests."""\n    install_opener(build_opener(TestHTTPHandler))\n    os.chdir(TEST_FOLDER)\n    \ndef teardown():\n    """Restore the normal HTTP handler."""\n    install_opener(build_opener(HTTPHandler))\n    # Go back to the original folder.\n    os.chdir(ORIGINAL_FOLDER)\n    # Delete the test folder.\n    shutil.rmtree(TEST_FOLDER)\n\ndef test_download1():\n    file = download("http://example.com/file.txt")\n    # Check that the file has been downloaded.\n    assert os.path.exists(file)\n    # Check that the file contains the contents of the remote file.\n    with open(file, \'r\') as f:\n        contents = f.read()\n    print(contents)\n    assert contents == \'test\'\n')


# ## Launching the tests

# In[ ]:


get_ipython().system('nosetests')


# ## Adding a failing test

# Now, let's add a new test.

# In[ ]:


get_ipython().run_cell_magic('writefile', 'test_datautils.py -a', '\ndef test_download2():\n    file = download("http://example.com/")\n    assert os.path.exists(file)\n')


# In[ ]:


get_ipython().system('nosetests')


# ## Fixing the failing test

# The new test fails because the filename cannot be inferred from the URL, so we need to handle this case.

# In[ ]:


get_ipython().run_cell_magic('writefile', 'datautils.py', '# Version 2.\nimport os\nfrom urllib.request import urlopen  # Python 2: use urllib2\n\ndef download(url):\n    """Download a file and save it in the current folder.\n    Return the name of the downloaded file."""\n    # Get the filename.\n    file = os.path.basename(url)\n    # Fix the bug, by specifying a fixed filename if the URL \n    # does not contain one.\n    if not file:\n        file = \'downloaded\'\n    # Download the file unless it already exists.\n    if not os.path.exists(file):\n        with open(file, \'w\') as f:\n            f.write(urlopen(url).read())\n    return file\n')


# In[ ]:


get_ipython().system('nosetests')


# > You'll find all the explanations, figures, references, and much more in the book (to be released later this summer).
# 
# > [IPython Cookbook](http://ipython-books.github.io/), by [Cyrille Rossant](http://cyrille.rossant.net), Packt Publishing, 2014 (500 pages).