What is the most convincing way to require formalized unit testing?

A very convincing way is to do formalized unit test yourself, regardless of what your team/company does. This might take some extra effort on your side, especially if you're not experienced with this sort of practice.

When you can then show your code is better and you are being more productive than your fellow developers, they are going to want to know why. Then feed them your favorite unit testing methods.

Once you've convinced your fellow developers, convince management together.

I use Maven with the Surefire and Cobertura plugins for all my builds. The actual test cases are created with JUnit, DbUnit and EasyMock.

Identifying Unit Tests I try to follow Test Driven Development but to be honest I usually just do that for the handful of the test cases and then come back and create tests for the edge and exception cases later.

Identifying Test Data DbUnit is great for loading test data for your unit tests.

Writing Test Cases I use JUnit to create the test cases. I try to write self documenting test cases but will use Javadocs to comment something that is not obvious.

Tracking & Making The Results Available I integrate the unit testing into my Maven build cycle using the Surefire plugin and I use the Corbertura plugin to measure the coverage achieved by those tests. I always generate and publish a web-site including the Surefire and Cobertura reports as part of my daily build so I can see what tests failed/passed.

The event which convinced me was when we managed to regress a bug three times, in three consecutive releases. Once I realised how much more productive I was as a programmer when I wasn't constantly fixing trivial mistakes after they had gone to the client, and I could have a warm fuzzy feeling that colleagues code would do what they claimed it would, I became a convert.