<html lang="en">

<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">

<meta charset="utf-8">

<meta http-equiv="X-UA-Compatible" content="IE=edge">

<meta name="viewport" content="width=device-width, initial-scale=1.0">

<meta name="author" content="Matt Makai">

<meta name="description" content="Unit testing exercises one function isolated from a program. Learn more about unit testing on Full Stack Python.">

<link rel="shortcut icon" href="//static.fullstackpython.com/fsp-fav.png">

<title>Unit Testing - Full Stack Python</title>

<!--[if lt IE 9]>

<link href="theme/css/f.min.css" rel="stylesheet">

<div style="padding: 0 0 20px 0; margin: 0 0 20px 0; background-color: #22B24C;">

<div class="container">

<h2 style="color: #fff; margin: 20px 40px 0 0;"><a href="https://www.gumroad.com/l/python-deployments" style="color: #fff">The Full Stack Python Guide to Deployments book</a> has been released!</h2>

</div>

</div> <a href="https://github.com/makaimc/fullstackpython.com"><img style="position: absolute; top: 0; right: 0; border: 0;" src="/theme/img/fork.png" alt="Fork me on GitHub"></a>

<div class="container">

<div class="row">

<div class="col-md-12">

<div class="logo-header-section">

<a href="/" style="text-decoration: none; border: none;"><img src="theme/img/logo.png" height="52" width="52" class="logo-image" style="padding-top: 1px;" alt="Full Stack Python logo"></a>

<span class="logo-title"><a href="/">Full Stack Python</a></span>

</div>

</div>

</div><div class="row">

<div class="col-md-8">

<h1>Unit testing</h1>

<p>Unit testing is a method of determining the correctness of a single function

isolated from a larger codebase. The idea is that if all the atomic units

of an application work as intended in isolation, then integrating them

together as intended is much easier.</p>

<h2>Why is unit testing important?</h2>

<p>Unit testing is just one form of <a href="/testing.html">testing</a> that works in

combination with other testing approaches to wring out the bugs from a

piece of software being developed. When several functions and classes are

put together it's often difficult to determine the source of a problem if

several bugs are occurring at the same time. Unit testing helps eliminate

as many of the individual bugs as possible so when the application comes

together as a whole the separate parts work as correct as possible. Then

when issues arise they can often be tracked down as unintended consequences

of the disparate pieces not fitting together properly.</p>

<h2>Unit testing tools</h2>

<p>There are many tools for creating tests in Python. Some of these tools, such

as pytest, replace the built-in unittest framework. Other tools, such as

nose, are extensions that ease test case creation. Note that many of these

tools are also used for <a href="/integration-testing.html">integration testing</a>

by writing the test cases to exercise multiple parts of code at once.</p>

<p><a href="https://docs.python.org/3/library/unittest.html">unittest</a>

is the built-in standard library tool for testing Python code.</p>

<p><a href="http://pytest.org/latest/">pytest</a> is a complete testing tool that

emphasizes backwards-compatibility and minimizing boilerplate code.</p>

<p><a href="https://nose.readthedocs.org/en/latest/">nose</a> is an extension to

unittest that makes it easier to create and execute test cases.</p>

<p><a href="https://github.com/Yelp/Testify/">testify</a> was a testing framework

meant to replace the common unittest+nose combination. However, the team

behind testify is transitioning to pytest so it's recommended you do

not use testify for new projects.</p>

<h3>Unit testing resources</h3>

<p><a href="https://realpython.com/blog/python/the-minimum-viable-test-suite/">The Minimum Viable Test Suite</a>

shows how to set unit tests and integration tests for a Flask example

application.</p>

<p><a href="http://www.diveintopython3.net/unit-testing.html">Dive into Python 3's chapter on unit testing</a>

has a complete example with code and a detailed explanation for creating

unit testing with the

<a href="https://docs.python.org/3/library/unittest.html">unittest</a> module.</p>

<p><a href="https://jeffknupp.com/blog/2013/12/09/improve-your-python-understanding-unit-testing/">Understanding unit testing</a>

explains why testing is important and shows how to do it effectively in

your applications.</p>

<p><a href="http://www.drdobbs.com/testing/unit-testing-with-python/240165163">Unit testing with Python</a>

provides a high-level overview of testing and has diagrams to demonstrate

what's going on in the testing cycle.</p>

<p>The Python wiki has a page with a list of

<a href="https://wiki.python.org/moin/PythonTestingToolsTaxonomy">Python testing tools and extensions</a>.</p>

<p><a href="http://blog.fogcreek.com/working-effectively-with-unit-tests-interview-with-jay-fields/">Working Effectively with Unit Tests</a>

is an interview with the author of a book by the title where he shares

some of the insight he's learned on the topic.</p>

<p><a href="http://blog.kevinastone.com/generate-your-tests.html">Generate your tests</a>

shows how to write a test generator that works with the <code>unittest</code>

framework.</p>

<h3>What else do you want to learn about testing?</h3>

<div class="row">

<div class="col-md-4">

<div class="well select-next">

<a href="/code-metrics.html" class="btn btn-success btn-full"><svg width="28" height="30" viewBox="0 0 1792 1792" xmlns="http://www.w3.org/2000/svg"><path d="M1596 380q28 28 48 76t20 88v1152q0 40-28 68t-68 28h-1344q-40 0-68-28t-28-68v-1600q0-40 28-68t68-28h896q40 0 88 20t76 48zm-444-244v376h376q-10-29-22-41l-313-313q-12-12-41-22zm384 1528v-1024h-416q-40 0-68-28t-28-68v-416h-768v1536h1280zm-1024-864q0-14 9-23t23-9h704q14 0 23 9t9 23v64q0 14-9 23t-23 9h-704q-14 0-23-9t-9-23v-64zm736 224q14 0 23 9t9 23v64q0 14-9 23t-23 9h-704q-14 0-23-9t-9-23v-64q0-14 9-23t23-9h704zm0 256q14 0 23 9t9 23v64q0 14-9 23t-23 9h-704q-14 0-23-9t-9-23v-64q0-14 9-23t23-9h704z" fill="#fff"/></svg></a>

<p class="under-btn">What code metrics should I be aware of?</p> </div>

</div>

<div class="col-md-4">

<div class="well select-next">

<a href="/testing.html" class="btn btn-success btn-full"><svg width="28" height="30" viewBox="0 0 1792 1792" xmlns="http://www.w3.org/2000/svg"><path d="M1280 1024h305q-5 6-10 10.5t-9 7.5l-3 4-623 600q-18 18-44 18t-44-18l-624-602q-5-2-21-20h369q22 0 39.5-13.5t22.5-34.5l70-281 190 667q6 20 23 33t39 13q21 0 38-13t23-33l146-485 56 112q18 35 57 35zm512-428q0 145-103 300h-369l-111-221q-8-17-25.5-27t-36.5-8q-45 5-56 46l-129 430-196-686q-6-20-23.5-33t-39.5-13-39 13.5-22 34.5l-116 464h-423q-103-155-103-300 0-220 127-344t351-124q62 0 126.5 21.5t120 58 95.5 68.5 76 68q36-36 76-68t95.5-68.5 120-58 126.5-21.5q224 0 351 124t127 344z" fill="#fff"/></svg></a>

<p class="under-btn">How do I go about testing my Python code?</p> </div>

</div>

<div class="col-md-4">

<div class="well select-next">

<a href="/continuous-integration.html" class="btn btn-success btn-full"><svg width="28" height="30" viewBox="0 0 1792 1792" xmlns="http://www.w3.org/2000/svg"><path d="M1639 1056q0 5-1 7-64 268-268 434.5t-478 166.5q-146 0-282.5-55t-243.5-157l-129 129q-19 19-45 19t-45-19-19-45v-448q0-26 19-45t45-19h448q26 0 45 19t19 45-19 45l-137 137q71 66 161 102t187 36q134 0 250-65t186-179q11-17 53-117 8-23 30-23h192q13 0 22.5 9.5t9.5 22.5zm25-800v448q0 26-19 45t-45 19h-448q-26 0-45-19t-19-45 19-45l138-138q-148-137-349-137-134 0-250 65t-186 179q-11 17-53 117-8 23-30 23h-199q-13 0-22.5-9.5t-9.5-22.5v-7q65-268 270-434.5t480-166.5q146 0 284 55.5t245 156.5l130-129q19-19 45-19t45 19 19 45z" fill="#fff"/></svg></a>

<p class="under-btn">Can I automate testing and deployments for my app?</p> </div>

</div>

</div><div id="mc_embed_signup">

<form action="//mattmakai.us2.list-manage.com/subscribe/post?u=b7e774f0c4f05dcebbfee183d&amp;id=b22335388d" method="post" id="mc-embedded-subscribe-form" name="mc-embedded-subscribe-form" class="validate" target="_blank" novalidate>

<div id="mc_embed_signup_scroll">

<h4>Sign up here to receive an email with major updates to this site and Python tutorials delivered to your inbox once a month.</h4>

<div class="row">

<div class="col-md-9">

<input type="email" value="" name="EMAIL" class="email form-control" id="mce-EMAIL" placeholder="email address" required>

<div style="position: absolute; left: -5000px;"><input type="text" name="b_b7e774f0c4f05dcebbfee183d_b22335388d" tabindex="-1" value=""></div>

</div>

<div class="col-md-3">

<div class="clear"><input type="submit" value="Subscribe" name="subscribe" id="mc-embedded-subscribe" class="btn btn-success" style="font-family: 'Helvetica Neue';"></div>

</div>

</div>

</div>

</div>

<div class="col-md-offset-1 col-md-3" id="sidebar">

<div class="panel panel-success">

<div class="panel-body">

<a href="http://www.deploypython.com/"><img src="//static.fullstackpython.com/fsp-deployment-guide.png" alt="The Full Stack Python Guide to Deployments" width="100%"></a>

<p style="font-size: .8em; margin-top: 10px;">Searching for a complete, step-by-step deployment walkthrough? Learn more about <a href="http://www.deploypython.com/">The Full Stack Python Guide to Deployments book</a>.

</p>

</div>

</div> <div class="panel panel-success">

<div class="panel-heading">

<h3 class="panel-head"><a href="/table-of-contents.html" style="color: #fff;">Table of Contents</a></h3>

</div>

<div class="list-group">

<a href="/introduction.html" class="list-group-item smaller-item " style='font-family: "Helvetica Neue",sans-serif;'>Introduction</a>

<a href="/learning-programming.html" class="list-group-item smaller-item " style='font-family: "Helvetica Neue",sans-serif;'>Learning Programming</a>

<a href="/why-use-python.html" class="list-group-item smaller-item " style='font-family: "Helvetica Neue",sans-serif;'>Why Use Python?</a>

<a href="/python-2-or-3.html" class="list-group-item smaller-item " style='font-family: "Helvetica Neue",sans-serif;'>Python 2 or 3?</a>

<a href="/enterprise-python.html" class="list-group-item smaller-item " style='font-family: "Helvetica Neue",sans-serif;'>Enterprise Python</a>

<a href="/best-python-resources.html" class="list-group-item smaller-item " style='font-family: "Helvetica Neue",sans-serif;'>Best Python Resources</a>

<a href="/best-python-videos.html" class="list-group-item smaller-item " style='font-family: "Helvetica Neue",sans-serif;'>Best Python Videos</a>

<a href="/development-environments.html" class="list-group-item smaller-item " style='font-family: "Helvetica Neue",sans-serif;'>Development Environments</a>

<a href="/vim.html" class="list-group-item smaller-item " style='font-family: "Helvetica Neue",sans-serif;'>Vim</a>

<a href="/emacs.html" class="list-group-item smaller-item " style='font-family: "Helvetica Neue",sans-serif;'>Emacs</a>

<a href="/generators.html" class="list-group-item smaller-item " style='font-family: "Helvetica Neue",sans-serif;'>Generators</a>

<a href="/comprehensions.html" class="list-group-item smaller-item " style='font-family: "Helvetica Neue",sans-serif;'>Comprehensions</a>

<a href="/web-frameworks.html" class="list-group-item smaller-item " style='font-family: "Helvetica Neue",sans-serif;'>Web Frameworks</a>

<a href="/django.html" class="list-group-item smaller-item " style='font-family: "Helvetica Neue",sans-serif;'>Django</a>

<a href="/flask.html" class="list-group-item smaller-item " style='font-family: "Helvetica Neue",sans-serif;'>Flask</a>

<a href="/bottle.html" class="list-group-item smaller-item " style='font-family: "Helvetica Neue",sans-serif;'>Bottle</a>

<a href="/pyramid.html" class="list-group-item smaller-item " style='font-family: "Helvetica Neue",sans-serif;'>Pyramid</a>

<a href="/morepath.html" class="list-group-item smaller-item " style='font-family: "Helvetica Neue",sans-serif;'>Morepath</a>

<a href="/other-web-frameworks.html" class="list-group-item smaller-item " style='font-family: "Helvetica Neue",sans-serif;'>Other Web Frameworks</a>

<a href="/web-design.html" class="list-group-item smaller-item " style='font-family: "Helvetica Neue",sans-serif;'>Web Design</a>

<a href="/cascading-style-sheets.html" class="list-group-item smaller-item " style='font-family: "Helvetica Neue",sans-serif;'>Cascading Style Sheets</a>

<a href="/javascript.html" class="list-group-item smaller-item " style='font-family: "Helvetica Neue",sans-serif;'>JavaScript</a>

<a href="/websockets.html" class="list-group-item smaller-item " style='font-family: "Helvetica Neue",sans-serif;'>WebSockets</a>

<a href="/web-application-security.html" class="list-group-item smaller-item " style='font-family: "Helvetica Neue",sans-serif;'>Web Application Security</a>

<a href="/static-site-generator.html" class="list-group-item smaller-item " style='font-family: "Helvetica Neue",sans-serif;'>Static Site Generators</a>

<a href="/data.html" class="list-group-item smaller-item " style='font-family: "Helvetica Neue",sans-serif;'>Data</a>

<a href="/databases.html" class="list-group-item smaller-item " style='font-family: "Helvetica Neue",sans-serif;'>Databases</a>

<a href="/no-sql-datastore.html" class="list-group-item smaller-item " style='font-family: "Helvetica Neue",sans-serif;'>NoSQL Data Stores</a>

<a href="/object-relational-mappers-orms.html" class="list-group-item smaller-item " style='font-family: "Helvetica Neue",sans-serif;'>Object-relational Mappers (ORMs)</a>

<a href="/application-programming-interfaces.html" class="list-group-item smaller-item " style='font-family: "Helvetica Neue",sans-serif;'>Application Programming Interfaces</a>

<a href="/api-integration.html" class="list-group-item smaller-item " style='font-family: "Helvetica Neue",sans-serif;'>API Integration</a>

<a href="/api-creation.html" class="list-group-item smaller-item " style='font-family: "Helvetica Neue",sans-serif;'>API Creation</a>

<a href="/deployment.html" class="list-group-item smaller-item " style='font-family: "Helvetica Neue",sans-serif;'>Deployment</a>

<a href="/servers.html" class="list-group-item smaller-item " style='font-family: "Helvetica Neue",sans-serif;'>Servers</a>

<a href="/platform-as-a-service.html" class="list-group-item smaller-item " style='font-family: "Helvetica Neue",sans-serif;'>Platform-as-a-service</a>

<a href="/operating-systems.html" class="list-group-item smaller-item " style='font-family: "Helvetica Neue",sans-serif;'>Operating Systems</a>

<a href="/web-servers.html" class="list-group-item smaller-item " style='font-family: "Helvetica Neue",sans-serif;'>Web Servers</a>

<a href="/wsgi-servers.html" class="list-group-item smaller-item " style='font-family: "Helvetica Neue",sans-serif;'>WSGI Servers</a>

<a href="/source-control.html" class="list-group-item smaller-item " style='font-family: "Helvetica Neue",sans-serif;'>Source Control</a>

<a href="/application-dependencies.html" class="list-group-item smaller-item " style='font-family: "Helvetica Neue",sans-serif;'>Application Dependencies</a>

<a href="/static-content.html" class="list-group-item smaller-item " style='font-family: "Helvetica Neue",sans-serif;'>Static Content</a>

<a href="/task-queues.html" class="list-group-item smaller-item " style='font-family: "Helvetica Neue",sans-serif;'>Task Queues</a>

<a href="/configuration-management.html" class="list-group-item smaller-item " style='font-family: "Helvetica Neue",sans-serif;'>Configuration Management</a>

<a href="/continuous-integration.html" class="list-group-item smaller-item " style='font-family: "Helvetica Neue",sans-serif;'>Continuous Integration</a>

<a href="/logging.html" class="list-group-item smaller-item " style='font-family: "Helvetica Neue",sans-serif;'>Logging</a>

<a href="/monitoring.html" class="list-group-item smaller-item " style='font-family: "Helvetica Neue",sans-serif;'>Monitoring</a>

<a href="/web-analytics.html" class="list-group-item smaller-item " style='font-family: "Helvetica Neue",sans-serif;'>Web Analytics</a>

<a href="/docker.html" class="list-group-item smaller-item " style='font-family: "Helvetica Neue",sans-serif;'>Docker</a>

<a href="/caching.html" class="list-group-item smaller-item " style='font-family: "Helvetica Neue",sans-serif;'>Caching</a>

<a href="/microservices.html" class="list-group-item smaller-item " style='font-family: "Helvetica Neue",sans-serif;'>Microservices</a>

<a href="/testing.html" class="list-group-item smaller-item " style='font-family: "Helvetica Neue",sans-serif;'>Testing</a>

<a href="/unit-testing.html" class="list-group-item smaller-item active" style='font-family: "Helvetica Neue",sans-serif;'>Unit Testing</a>

<a href="/integration-testing.html" class="list-group-item smaller-item " style='font-family: "Helvetica Neue",sans-serif;'>Integration Testing</a>

<a href="/code-metrics.html" class="list-group-item smaller-item " style='font-family: "Helvetica Neue",sans-serif;'>Code Metrics</a>

<a href="/debugging.html" class="list-group-item smaller-item " style='font-family: "Helvetica Neue",sans-serif;'>Debugging</a>

<a href="/what-full-stack-means.html" class="list-group-item smaller-item " style='font-family: "Helvetica Neue",sans-serif;'>What "Full Stack" Means</a>

<a href="/change-log.html" class="list-group-item smaller-item " style='font-family: "Helvetica Neue",sans-serif;'>Change Log</a>

<a href="/future-directions.html" class="list-group-item smaller-item " style='font-family: "Helvetica Neue",sans-serif;'>Future Directions</a>

<a href="/about-author.html" class="list-group-item smaller-item " style='font-family: "Helvetica Neue",sans-serif;'>About the Author</a>

</div>

</div>

<div class="panel panel-success">

<div class="panel-body">

<a href="http://www.deploypython.com/"><img src="//static.fullstackpython.com/fsp-deployment-guide.png" alt="The Full Stack Python Guide to Deployments" width="100%"></a>

<p style="font-size: .8em; margin-top: 10px;">Searching for a complete, step-by-step deployment walkthrough? Learn more about <a href="http://www.deploypython.com/">The Full Stack Python Guide to Deployments book</a>.

</p>

</div>

</div> <div class="panel panel-success">

<div class="panel-heading"><h3 class="panel-head">Unit Testing</h3></div>

<div class="panel-body">

Major updates are tweeted via

<a href="https://twitter.com/fullstackpython">@fullstackpython</a>.

<hr/>

Need more detailed tutorials than you see here?

<a href="http://www.deploypython.com/">Learn more about The Full Stack Python Guide to Deployments book.</a>

</div>

</div>

<hr/>

</div>

<div class="container">

<div class="footer pull-right">

<a href="http://www.mattmakai.com/" class="underline">Matt Makai</a>

2015

</div>

</div>

(function(i,s,o,g,r,a,m){i['GoogleAnalyticsObject']=r;i[r]=i[r]||function(){

(i[r].q=i[r].q||[]).push(arguments)},i[r].l=1*new Date();a=s.createElement(o),

m=s.getElementsByTagName(o)[0];a.async=1;a.src=g;m.parentNode.insertBefore(a,m)

})(window,document,'script','//www.google-analytics.com/analytics.js','ga');

ga('create', 'UA-19910497-7', 'auto');

ga('send', 'pageview');

<script type='text/javascript'>

var trackOutboundLink = function(url) { ga('send', 'event', 'outbound', 'click', url, {'hitCallback': function () { document.location = url; } }); }