"increasing" and "decreasing" should be specified better. ATM, testing is so limited it allows for solving with a third category "constant" - this may or may not even be intentional.

Needs random test cases, refer to this for examples :)

Needs random test cases

Similar to the "Overlapping Ranges" kata, please use the Test.assertEquals method. This at least makes it easy to see what the error was.

Another suggestion is I highly recommend wrapping your tests in describe and it blocks (in both Katas). This enables more than one test to run before bailing.

BTW: bkaes has put together an amazing document about writing good Katas. Definitely worth a read!

Also, I believe the answer for this test is off-by-one. It states the index should be 3, but at the index 3 we're still increasing:

idx:  0   1   2   3   4   5   6
arr:  1   2   4   6   4   3   1
dir:    +   +   +   -   -   -

It is a matter of opinion as to where the result should be, but it really seems like the first number that changes the pattern is at index 4.

Your description of the problem doesn't match the expected solution or code setup (it says you'll receive an array, but 5 unique arguments are passed in).

There's also no example test cases, which doesn't help.