QSSI, a part of UnitedHealth Group’s Optum unit, didn’t see full end-to-end testing until a few days before the launch. “Ideally,” said Andrew Slavitt, QSSI group executive vice president, “we would have loved to have months.”

CMS' apparent commitment to the October go-live date in the face of potential or known problems rankled a number of lawmakers.

“I’m very disturbed that CMS did not give you an adequate amount of time for testing,” Greg Walden, a Republican from Oregon, said, noting that the Oregon Department of Motor Vehicles’ database overhaul in the late 1980s was scrapped after some $50 million. That failed, and he doesn’t want the same to happen to Healthcare.gov, he said. “This isn't a partisan issue about healthcare. People expect this to work."

Illinois Republican John Shimkus, raising his voice a bit (he wasn’t the only one), wanted to know who at CMS was ultimately directing the testing. Campbell, a former SAIC vice president, listed CMS deputy CIO Henry Chao and COO Michelle Snyder.

The good news, Campbell said, is that the website is gradually improving. But how are they fixing it? asked California Democrat Henry Waxman. “Do you have to start from scratch and rewrite 5 million lines of code?”

No, Campbell said. “The 300-plus employees in the office would all walk out if I told them they had to rewrite that many lines of code.”