You're generating 1,500,000-elements-long sequence inside the fixture while the maximum tested number is 500,000. This makes the tests run a couple more seconds for no reason.

I don't understand the "floor" system. Following the numerotation it should be possible to have houseOfCards(0) === 2.
Also all the edge cases should be referenced with the correct way of handling them.

For the ones trying to complete the Kata, the function should throw an Error (Javascript object: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error) in the following cases:

• floors is not an integer (float/string/etc)
• floors is negative