This is from O'Reilly's Developer Notebook series. Although the series description says that these books are for early adopters of leading-edge and emerging technologies, I think the techniques discussed in this book have been around for a while. I know I've seen them used with many CPAN modules that I have downloaded over the last while. However, that issue speaks nothing to the usefulness of the book, and it is useful.
The book is a concise 180 pager that deals with Perl's Test::More and Test::Harness in particular, and some other modules along the way. The content is organized into various task oriented groupings, with little or no conceptual content (i.e. theory) at all.
Each task is composed in the following format, some items of which are optional:
The pages appear like grid paper, as a programmer might use to make notes on, though the content is still normally typeset fonts following a standard convention. Each chapter's first page is complete with the same coffee stain that appears on the cover.
In addition, the margins often have text in a font meant to mimick hastily written notes. The major problem with the notes is that they can be difficult to read. This is partly to do with the appearance of the font used - some characters look too much like others - and the habit of breaking lines at non-whitespace - an issue for module names and such.
At first, the testing appeared to be geared only to testing modules and subroutines. Fortunately, I did read through to the end and found that, close to the end, even interactive programs were addressed. In between, you could find testing methods for everything from databases and network apps, to POD documentation and unit tests.
This book is very useful for testers, and even programmers themselves, particularly if they intend to distribute their code (i.e. CPAN). If anything, I felt there was room for more content, rather than directing the reader to other resources. I would have liked to see more right there.