If you do, do you discuss coverage, continuous integration, quality control, or anything related to the difference between unit testing, functional testing and TDD in general? If clients ask, do you simply state that you will unit test, but leave out specifics?
Do you write unit testing or TDD as a line item requirement into your contracts or statements of work?
unit testing;tdd;continuous integration
IMO,unit testing is akin to an implementation detail. They are hidden, yet quite an unwritten expectation.  TDD would fall into this category as well since, again, it is really a process of software development. The contract defines expectations, not a process.  If a summary of time is expected, these should generally fall into categories of Design and Testing.