apparently, not closing LIs and Ps is also a hard habit to break

unit-testing.html

@@ -27,7 +27,7 @@ body{counter-reset:h1 8}
 <li>There is no way to represent negative numbers in Roman numerals.
 <li>There is no way to represent fractions or non-integer numbers in Roman numerals.
 </ol>
-<p>Let&#8217;s start mapping out what a <code>roman.py</code> module should do.  It will have two main functions, <code>to_roman()</code> and <code>from_roman()</code>. The <code>to_roman()</code> function should take an integer from <code>1</code> to <code>3999</code> and return the Roman numeral representation as a string&hellip;</p>
+<p>Let&#8217;s start mapping out what a <code>roman.py</code> module should do.  It will have two main functions, <code>to_roman()</code> and <code>from_roman()</code>. The <code>to_roman()</code> function should take an integer from <code>1</code> to <code>3999</code> and return the Roman numeral representation as a string&hellip;
 <p>Stop right there. Now let&#8217;s do something a little unexpected: write a test case that checks whether the <code>to_roman()</code> function does what you want it to. You read that right: you&#8217;re going to write code that tests code that you haven&#8217;t written yet.
 <p>This is called <i>unit testing</i>.  The set of two conversion functions &mdash; <code>to_roman()</code>, and later <code>from_roman()</code> &mdash; can be written and tested as a unit, separate from any larger program that imports them. Python has a framework for unit testing, the appropriately-named <code>unittest</code> module.
 <p>Unit testing is an important part of an overall testing-centric development strategy. If you write unit tests, it is important to write them early (preferably before writing the code that they test), and to keep them updated as code and requirements change. Unit testing is not a replacement for higher-level functional or system testing, but it is important in all phases of development: