Setting action plans and goals of individual developers.

As a manager of small team it's expected from me to set clear and easy do measure actions or goals of my developers. Let me jump straight to examples.

Problem 1: developers are not writing tests.

Solution proposed by my director: set hard rule (metric) that there must 80% code coverage by the end of next month.

Solution by me: work with developers and genuinely change their mindset so they understand importance of tests.

Problem 2: developer is commiting code once per week, resulting in 200+ files pull request.

Solution proposed by my director: set him a goal that PR should contain maximum number of N (put any fixed number here) changes or files.

Solution proposed by me: coach developer on importance of frequent and small Pull requests, monitor his progress and solve potential issues.

… there are more, but all have similar pattern: My supervisors are almost always proposing a Numeric solution, and me to go after them and check if the numbers are met (that sounds like micromanagement, doesn't it?), while I argue with them that only genuine change in one's mind make sense, and numeric value is of secondary (or even less) importance.

What do you think? What's your experience on it?