The standard Test::Tutorial is a must-read.

The POD in Test::Simple and Test::More is well-written.

And the following perl.com articles by chromatic are excellent: Testing, Test::MockObject

In addition to trammell's suggestions above, for specification-based testing, tmoertel's Test::LectroTest is an excellent tool.

Test::LectroTest allows you to autmatically generate data-sets that tests larger areas of the problem space with ease. Read the module author's tutorial on the subject for a nice primer.

For books, see

• Perl Testing: A Developer's Notebook walks you through the entire testing setup and procedure, many practical tips for using the various testing modules and strategies.
• Advanced Perl Programming 2ed has a chapter dedicated to testing.
• Perl Best Practices also has a chapter dedicated to testing and debugging.

Effective Perl Programming, 2d ed ISBN 9780321496942, published in 2010, has a chapter on testing. It is not a tutorial on basic test techniques. It includes several multi-page examples; and covers topics such as mock objects, test-driven development, and a continuous build system.

Perl Medic, Transforming Legacy Code ISBN 9780201795264 from 2004, also has a chapter on testing. It provides short introductions to several Test:: modules; and a detailed description of how to build real test code with a well-written 15-page example.

Perl Testing, a Developer's Notbook by Langworth and Chromatic; [O'Reilly]

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I Go Back to Sleep, Now.

OGB