The flight test for A350-1000 will start this year (October) as the 97k lb -1000 engine will be flight tested on A380 like it was done for the -900 engine.
Testing will contain approximately 120h flight hours where also certain engine certification test will be completed.
This is a lesson learnt from A350-900 as it contributed to risk reduction and a smooth flight test.
Flight testing of the 1st complete A350-1000 will start next summer (probably in September) and span a 9 month test program with 3 test aircraft (MSN59, MSN65 and MSN71) flying a total of 1500 hours.
Certification is foreseen for Q2 2017 followed by first customer delivery in summer 2017.