Writing a Test Plan

Dear KV,

We are getting ready for a project release at work, and since we are a small startup, all the developers have been asked to test the code of one of the other developers. We did this by lottery, each of us drawing a name from a hat (we were not allowed to draw our own name). It was an odd way to select testers, but it seems no worse than the processes I have seen at larger companies. The problem for me is not that I have to write tests, but that I also have to write a test plan, one of the requirements imposed by our CEO, who is also the VP of engineering, aka my boss. I have never written an actual test plan, just collections of tests. Of course, I test my own code, but because I wrote the code, I know what I am testing, and it has always been a straightforward process. Should I just write the tests and then list them in the plan? Somehow that does not seem to be what my boss is looking for.