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<h1>Testing</h1>

<p>Testing determines whether software runs correctly based on specific inputs

and identifies defects that need to be fixed.</p>

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

<p>As software scales in codebase size, it's impossible for a person or even

a large team to keep up with all of the changes and

the interactions between the changes. Automated testing is the only proven

method for building reliable software once they grow past the point of a

simple prototype. Many major software program development failures can be

traced back to inadequate or a complete lack of testing.</p>

<p>It's impossible to know whether software works properly unless it is tested.

While testing can be done manually, by a user clicking buttons or typing in

input, it should be performed automatically by writing software programs that

test the application under test.</p>

<p>There are many forms of testing and they should all be used together. When

a single function of a program is isolated for testing, that is called

<a href="/unit-testing.html">unit testing</a>. Testing more than a single function

in an application at the same time is known as

<a href="/integration-testing.html">integration testing</a>.

<em>User interface testing</em> ensures the correctness of how a user would

interact with the software. There are even more forms of testing that large

programs need, such as <em>load testing</em>, <em>database testing</em>, and

<em>browser testing</em> (for web applications).</p>

<h2>Testing in Python</h2>

<p>Python software development culture is heavy on software testing. Because

Python is a dynamically-typed language as opposed to a statically-typed

language, testing takes on even greater importance for ensuring program

correctness.</p>

<h2>Testing resources</h2>

<ul>

<li>

<p><a href="http://late.am/post/2015/04/20/good-test-bad-test.html">Good test, bad test</a>

explains the difference between a "good" test case and one that is not

as useful. Along the way the post breaks down some myths about common

testing subjects such as code coverage, assertions and mocking.</p>

</li>

<li>

<p><a href="http://pythontesting.net/">Python Testing</a> is a site devoted to testing

in - you guessed it - the Python programming language.</p>

</li>

<li>

<p><a href="http://michaeldehaan.net/post/120522567217/the-case-for-test-driven-development">The case for test-driven development</a>

by Michael DeHaan explains how automation is the only way to build software

at a large scale.</p>

</li>

<li>

<p>Google has a <a href="http://googletesting.blogspot.com/">testing blog</a> where

they write about various aspects of testing software at scale.</p>

</li>

<li>

<p>Still confused about the difference between unit, functional and

integration tests? Check out this

<a href="http://stackoverflow.com/questions/4904096/whats-the-difference-between-unit-functional-acceptance-and-integration-test">top answer on Stack Overflow</a>

to that very question.</p>

</li>

</ul>

<h3>What's next after testing your application?</h3>

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