The American outfit completed 167 laps on the final day in Barcelona - with Grosjean completing 73 of them in the morning session and his team-mate Kevin Magnussen taking over from him later on in the day for the rest.
Magnussen even managed to set a personal best of 1:17.565 on the C5 tyre compound as Haas showed off their pace in Spain.
"It's been a good morning," Grosjean said to the Checkered Flag. "We ran our full programme, which is very positive. We're finding a bit more time in the car, run-after-run, which is great.
"I'm generally happy with winter testing to-date. Maybe we have had a few more issues than we'd have liked, but if we react well and sort them out, there are many things we've ticked in the box."
The Frenchman believes his side have prepared in every way possible ahead of the new season, and now he has his eyes fully focused on the opening race of the season in Melbourne.
"I think we're ready for Melbourne, I'm looking forward to getting there," Grosjean concluded.