How to test software that burns CDs without wasting CDs

Copy-pasted and then edited test cases are often fine.

Tests should have as few external dependencies as possible, and be as straightforward as possible. Test cases tend to change with time, and previously almost identical test cases may suddenly diverge. Updating one test case without having to worry about breaking other cases is a Good Thing.

Of course, boilerplate code which is identical in many test cases and has to change in concert can and should be factored out.

You've laid out good arguments for and against unit testing. So you have to ask yourself, "Do I see value in the positive arguments that outweigh the costs in the negative ones?" I certainly do:

• Small-and-fast is a nice aspect of unit testing, although by no means the most important.
• Locating-bug[s]-easier is extremely valuable. Many studies of professional software development have shown that the cost of a bug rises steeply as it ages and moves down the software-delivery pipeline.
• Finding-masked-bugs is valuable. When you know that a particular component has all of its behaviors verified, you can use it in ways that it was not previously used, with confidence. If the only verification is via integration testing, you only know that its current uses behave correctly.
• Mocking is costly in real-world cases, and maintaining mocks is doubly so. In fact, when mocking "interesting" objects or interfaces, you might even need tests that verify that your mock objects correctly model your real objects!

In my book, the pros outweigh the cons.