Toto Wolff has emphasised Mercedes cannot be complacent as it prepares to defend its Formula 1 World Championship titles, despite pre-season testing suggesting its advantage over the competition remains intact.

Speaking as 12 days of F1 testing drew to a conclusion at the Circuit de Catalunya, Mercedes heads to the Australian Grand Prix season opener having displayed a notable advantage in terms of raw pace, marking a continuation from its dominant 2014 display with Lewis Hamilton and Nico Rosberg.

Despite this, Wolff was keeping his expectations firmly in check, insisting that testing makes it difficult to read Mercedes' rivals, adding that he would rather view it as a 'glass half empty' situation.

"Testing is always very difficult to read, but it is looking good," he said. "Now it is about proving we can do the same on a race weekend. With the normal scepticism, we need to have the glass half empty. I think we can be optimistic."

Rosberg ended the test with the fastest time of 1min 22.7secs, achieved on soft tyres fitted to his W06. As a reference, Valtteri Bottas in the Williams managed a 1min 23.0secs on the super-soft tyres on the final day of testing.