The commercial product I'm working on has 92% code coverage --- but that's only if you consider the back-end code that we wrote.Â  I don't know what the coverage is of the libraries we're using (should I worry?), nor of the Javascript that makes the front end sing and dance (it's at least as complicated as the back-end code).Â  I'm not particularly worried by this --- it's higher coverage than most commercial projects I've worked on, and high enough that I'm confident there are no trivial-to-stumble-over bugs in our code.Â  I don't think I'd expect any more from scientific codes...