Thank you for your input :)
Unfortunately I do not currently have the time to be active on Codewars, between dealing with a death in the family, and work.

Ouch, you are quite right, thank you for bringing this to my attention. It should be fixed now.

Now available in a new flavor: Javascript!

It might be interesting to have a low-level [higher kyu, smaller loops, no optimization needed] baby sibling of this kata for those of us not quite ready for this one.

You fixed it so fast I thought it was me who was sleepy and confused :) (which I am)

In ruby, tests (methods are written with underscores) do not match the camelcasing provided in the instructions and the starter solution.

I found the description somewhat baffling at first, but by playing around with the tests and looking at the wikipedia article, it all fell into place bit by bit.
I also had a timing out issue that didn't go away after correcting an obvious bug, yet went away mysteriously shortly afterwards, after (supposedly) cosmetic cleaning of my code.

Oh, and I very much enjoyed this kata :)

Nice kata, however the testing could be tightened up (see comments in my solution).

Thanks for your comment. In a little while I will add explanatory messages for all of the current tests (but add a few more tests without messages, to be on the safe side). I also just realized that I had added error messaging in Ruby but omitted to add them in Coffeescript :(

Meanwhile, a few comments about the issue you may be running into. The current 6th test is for the determinant of a 4x4 matrix, so if you are using the formula for a 3x3 matrix alone, it is bound to not work. If you are using it to calculate determinants of larger matrix by considering 3x3 minors, that should be fine, if overkill. Also, a general comment, Codewars supports using "puts" (or console.log in Coffeescript) messages so you can use these to find input values when it is unclear why tests are failing.

Edit -- tests updated.

An interesting and challenging kata.

Nice :) Perhaps in " it must throw an error in order to remember Santa" remember should be remind?

6 kyu, or 7? I vacillated, but went with 6 in the end, mainly because of throwing an error.

Thanks for your feedback, I have switched to Test.assertEquals with explanatory messages for the first few tests.

Nice kata!