Interesting that the authors concluded there's no strong causal relationship between unit test coverage and the number of defects or perceived code quality. I

Interesting that the authors concluded there's no strong causal relationship between unit test coverage and the number of defects or perceived code quality. I felt that perhaps defects detected by tests during original coverage might have been overlooked. It seems they were examining the defects detected by only increasing coverage. Maybe some of the code coverage they studied were simple smoke tests without much granularity. Code quality perception is probably very subjective.