But who volunteered to do the taste test?

The AP has a story by Mike Schneider:

After several days without luck, astronauts finally ran a successful test on equipment that turns urine into drinking water — a necessity for supporting the international space station's crew, which will soon double. "Not to spoil anything, but I think up here the appropriate words are 'Yippee!'" space station commander Mike Fincke told Mission Control early Tuesday morning, shortly before bedtime. "There will be dancing later," Mission Control replied.
Astronauts had spent a frustrating five days trying to get the urine processor working. But, until early Tuesday, the machine couldn't last the four hours needed for a successful test run. Another urine processor test was planned later Tuesday, shortly after the seven astronauts on the docked space shuttle Endeavour and the three space station crew members woke up.
NASA added a sixteenth day to Endeavour's mission so astronauts could tinker with the urine processor before the shuttle returns to Earth, possibly with the troubled equipment packed aboard. NASA managers had debated bringing part of the contraption back to Earth for repairs if tests weren't successful. Endeavour is now set to undock Friday and land in Florida on Sunday.
The urine processor makes up a section of the $154 million water recycling system that was delivered to the space station by Endeavour. The machine is crucial to providing drinking water for the space station's crew, which is supposed to double to six members next year. Samples of the processed urine, sweat, and condensation will be tested on Earth before astronauts can start drinking the purified water next year.
In an effort to fix the problem, Fincke and Endeavour astronaut Don Pettit had removed vibration grommets which were used to mount a centrifuge in the urine processor, and bolted the piece down. The Endeavour astronauts on Tuesday also were to find out if the four spacewalks they performed during the mission paid dividends. The focus of the four spacewalks was cleaning and lubricating a jammed solar-wing joint on the station's right side. Flight controllers sent commands to make the joint rotate twice while the crew slept. Mission Control said the early morning test was proceeding well. That joint had not worked properly for more than a year, preventing the solar wings on that side from pointing automatically toward the sun to generate electricity. Grinding parts left the joint full of metal shavings that kept it from rotating.
The station's crew members and Endeavour's astronauts were told to tiptoe around the orbiting complex if they woke up in the middle of the night so as not to create vibrations during the test. Astronauts were given an extra half hour to sleep in because of the test. "No early risers tomorrow, apparently," Fincke said Monday night.