I am going to provide a real-world example of why tests are very important, based on a situation I ran into today.

I wanted to make some changes to my XS-based Bit::Manip distribution. One of my goals was to replace calls to stdint.h's pow() function with bit shift operations instead, to remove the reliance on the external library.

With my full test suite in place, I could freely replace things like:

#define MULT 2
return ((int)pow(MULT, bits) - 1) << lsb;

[download]

With:

return ((1 << bits) - 1) << lsb;

[download]

...and not have to worry about a thing, because all I had to do was make the change, run the tests, and on fail, go back to the math. Once all tests passed, I knew I was good.

Without a test suite, how would I ever know if I'm 100% accurate in my modification? I wouldn't be. Because all of my subs are covered entirely, I know that one change there didn't break anything within the sub its defined in, nor does the change break anything far away either.

In reply to Re^3: Test Driven Development, for software and for pancakes by stevieb
in thread Test Driven Development, for software and for pancakes by talexb

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.