Q:

Can an A&P who is also a private pilot receive compensation for conducting maintenance test flights?

Related to this question.
Suppose a repair is made to an airplane and a maintenance test flight is required. Suppose the A&P who works on the aircraft is also a private pilot. That person performs the test flight and then signs off the repair.  (assume USA)
A private pilot can't fly for compensation or hire.
Can the mechanic bill for the time she spent flying?  Are maintenance test flights considered incidental to a mechanic's business?

A:

Yes, the mechanic can fly the aircraft, according to this FAA legal interpretation (Williams, 2014):

The scenario you present is a mechanic who, as part of his duties,
  conducts flight tests after performing maintenance on the aircraft,
  and does not carry passengers or property for compensation or hire.
  The mechanic holds a private pilot certificate with a valid third
  class medical certificate. This situation is covered under §
  61.113(b), which states that, "[a] private pilot may, for compensation or hire, act as pilot in command of an aircraft in connection with any
  business or employment if (1) the flight is only incidental to that
  business or employment and (2) the aircraft does not carry passengers
  or property for compensation or hire." As these flight tests are
  incidental to his employment as a mechanic, the mechanic is not in
  violation of § 61.113 when conducting these flight tests

