In our shop, we simply have Statement/branch coverage in excess of 90% as one of the checks in our CI system. If coverage statistic drops below that, the build fails, the developer responsible gets and emails, and all our build monitors turn red. No one else can check in code until that is fixed. Makes for very embarrassing situation for the dev that breaks things.
Myself included. If I write framework code and the unit test coverage of that drops below the threshold. I break the build and will have to fix it. We also have an unsaid rule, you don't go home on a red build.
Very Simple ensure that UNIT Test Results are published along with build which is released to any team QA/Business/etc. Set this as a build acceptance criteria. If no unit test results are published don't accept the build.
I don't build Software but I make them work better, Testing is a Passion