Ricardo Zonta has signed a one-year contract extension to stay as Toyota's test and reserve driver in 2006.
Zonta will attend races as a reserve for Trulli and Schumacher
Zonta said: "We enjoyed such a successful year in 2005 and I am sure this trend will continue. I feel part of the family at Toyota."
Toyota finished fourth overall in the 2005 championship, but the success means they will no longer be allowed to run a third car in Friday practice.
Zonta will attend races as a reserve for Jarno Trulli or Ralf Schumacher.
French veteran Olivier Panis will also continue as a test driver.
Toyota have three scheduled test sessions in Spain before the traditional winter break.
This week's test will also be their first with Bridgestone tyres after switching from this year's dominant manufacturer Michelin.
"It is important to get the partnership working as quickly as possible," said Toyota Motorsport president John Howett.
"The fact that we can test the new mechanical package and suspension together with V8 engine and Bridgestone rubber will surely give us a valuable head start."