Having retired from the last four straight Grands Prix - and suffered two separate technical glitches during the Austrian weekend - Alonso managed to put 104 laps on the board on day two in Spielberg, the highest tally McLaren have achieved over a single day this season.
With McLaren protege Stoffel Vandoorne racking up 76 laps on the first day, Alonso says McLaren now have enough data to drive the team on.
"The most important thing was to put some laps on the car after the problems we've had in the last couple of races," Alonso explained.
"I'm pretty happy with how the test has gone. Today was a positive day - we managed to complete more than 100 laps.
"Together with Stoffel's laps yesterday, I think we finished the test with some good information. Now, we need to go back to the factory and analyse everything, but we definitely have a lot of data to go forward with."
McLaren team manager Dave Redding said the team now have "positive momentum", particularly as they were able to evaluate a "range of new bodywork components" including the short-nose concept that Alonso trialled during over the weekend in Austria.
"Overall, we were able to make the most of the good weather and dry track conditions to complete solid sections of the test programme to our satisfaction," Redding added.
"Both days of the test have been productive - and most importantly, reliable - and we are now armed with lots of valuable data and useful feedback from both drivers, that we can take away and analyse in preparation for the next two races before the summer break."