In most software development groups I’ve worked, there have been at least one or two programmers who both believe in unit testing and have the discipline and knowledge to create good unit tests. This has not changed during my career.
I’ve seen a few groups where there are enough unit-test-infected programmers to create critical mass, and the entire group writes, maintains, and believes in unit tests.
I have seen even fewer companies that explicitly and consciously set out to build a group of programmers with the above critical mass in test-infectedness.
So I wonder if the majority of companies where good unit testing happens are the result of chance.
(in response to questions about Is unit testing doomed )