So three things happened with the unit test:
1) A red rectangle came up: "Looks like somebody already moved this post. Unit test post" (or something similar; it only showed up for a short moment).
2) The following results appeared:
Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US) AppleWebKit/534.10 (KHTML, like Gecko) Chrome/8.0.552.224 Safari/534.10
Move to today and check visible dates (0, 2, 2)
Move 1 week in the future and check visible dates (0, 2, 2)
Move 4 week in the future and check visible dates (0, 2, 2)
Move 8 week in the past and check visible dates (0, 2, 2)
Create a new post (0, 3, 3)
Get post information (0, 2, 2)
Change the date of an existing post (0, 2, 2)
Make a second change to the date of an existing post (0, 2, 2)
Edit the content of an existing post and mark it as scheduled (0, 2, 2)
Try to change a post date and fail because of a concurrency conflict (0, 2, 2)
Delete the post created for testing (0, 1, 1)
Tests completed in 14064 milliseconds.
22 tests of 22 passed, 0 failed.
3) The calendar started working again as it should directly after running the tests. So far, I have been unable to recreate the previous errors, even by logging out and back into the dashboard. I'm glad, of course, although unsure whether the bugs will return in the future, since I'm not sure how this got rid of them.
The only error listed in the java script console is a
"Failed to load resource: the server responded with a status of 404 (Not Found)"
on .../wp-content/plugins/edcal/lib/qunit.css . No errors appeared there during the previous malfunctions of the calendar before running the unit tests.