The Portuguese was given a day-and-a-half of running with Red Bull and, as well as setting competitive times, stayed out of trouble to get through his programme.
Although well aware that his F1 hopes still rest on him doing well in his Formula Renault 3.5 campaign, he says he has convinced himself this week that he is as prepared as he can be if he gets the nod for a move to Toro Rosso.
"I jumped out of the car after the last run today and I felt to myself, 'I'm ready. I want this'," explained da Costa.
"But like I said yesterday, it will all come down to the rest of my season in [Formula Renault 3.5]. We have to deserve a place in F1, and I want to deserve it properly.
"The timing is good, and I am in a good position, so I need to do my job properly. But I believe we can do it."
Da Costa feels that there is not much more he can do on track to prepare him better for a first F1 chance - and that the next step in his understanding will only come from racing.
"I am as ready as I can be," he said. "You only know how hard it can be once you have done it once at least.
"By having a few days like this, I feel like I am as ready as I can be. The only time you realise how hard it is, is actually when you do a race."
Da Costa said the focus of his work had been on helping Red Bull get a better understanding of the new Pirelli tyres, although he acknowledged that his own feedback on the matter was limited by the fact he had not run much with the 2013 construction.
However, he reckoned his performance in the car had been a positive for the team.
"To drive the car for half of the three days is a great chance, and a good sign that I am trusted by the team to carry out the work," he said. "And that is really good for me.
"To be working with a world champion team is the best you can have - learning with the best and working with the best.
"For me as a driver I am only gaining. I think in the team we got some good answers, so it is a step forward."