Are there any credible sources of information on the adoption of agile techniques like automated testing, continuous integration and refactoring?
Of those that are using unit testing, how many follow test first or test driven development.
I'm trying to determine how widespread these practices are.
This is a list of surveys about adoption of some of the technoques you asked: http://www.methodsandtools.com/dynpoll/vote.php
If you need a survey about adoption of agile methodology in general, this is a good article:
Agile adoption and penetration rates are being overestimated. Although the number of companies that are adopting agile practices is, indeed, reasonably high, most organizations use agile in a very small percentage of their overall work.
http://analytical-mind.com/2010/02/25/gartners-the-current-state-of-agile-method-adoption/
I know I am answering a question from 2011 in 2020, yet this appears on Google's first page when you query the topic. Nowadays, the closest I've found to answer the question regarding continuous integration and to be a "credible" source, is this study from Oregon State University in 2016:
Usage, Costs, and Benefits of Continuous Integration in Open-Source Projects http://cope.eecs.oregonstate.edu/papers/OpenSourceCIUsage.pdf
Where the conclusion states:
Our results show there are good reasons for the rise of CI. Compared to projects that do not use CI, projects that use CI: (i) release twice as often, (ii) accept pull requests faster, and (iii) have developers who are less worried about breaking the build. Therefore, it should come as no surprise that 70% of the most popular projects on GitHub heavily use CI.
The study takes into account 34,544 open-source projects from GitHub, (ii) 1,529,291 builds from the most commonly used CI system, and (iii) 442 survey respondents.
