Do test pilots on commercial aircraft wear a parachute?
To the best of my knowledge, all commercial aircraft being tested have their pilots take on parachutes and hi-vis clothing in addition to creating a possible means of egress on all important flights, such as the first flight and high-speed tests. 

Since getting the cabin doors open is practically difficult, the solution I think most producers use is to built a chute down the front cargo entrance which can open.

Bombardier produced a pretty extensive film for their new CSeries.

Here's the solution employed on the Concorde: