Unit-testing – Differences between software testing processes and techniques

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/

Your professor is right: unit testing can be either black-box or white-box. The difference is less about what the tester knows, but more about how you generate test cases.

With black box testing, you only look at the interface and (if it exists) the specification for a component. When a function has a signature int foo(int a, int b), then I can immediately generate a few test cases just by testing interesting integers: zero, one, minus one, multi-digit numbers, INT_MAX, INT_MAX - 1 and so on. Black box tests are great because they are independent from the implementation. But they might also miss important cases.

With a white-box test, I look at the implementation, i.e. the source code and generate test cases from that. For example, I might want to achieve 100% path coverage for a function. I then choose input values so that all paths are taken. White-box tests are great because they can exhaustively exercise a piece of code, with far more confidence than a black-box tests. But they might be only testing implementation details, not actually important behaviour. In some cases, they are clearly a waste of time.

Since a white-box test is derived from the implementation, it can only be written afterwards. A black-box test is derived from the design/interface/specification, and can therefore be written before or after the implementation. TDD is neither clearly black-box or white-box. Since all behaviour is first expressed by a test and then the minimal code for that behaviour is implemented, TDD results in similar test cases to a white box test. But when we look at the information flow, TDD tests are not derived from the source code, but from external requirements. Therefore, TDD is more black-box-like.