Rather than having both upper and lower case in the expression include the 'i' flag which will make the expression case-insensitive meaning it will match regardless of case.
"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.
The author's solution as it exists does weird things on them, so for now, no.
Should the plateaus be considered?
If so, test cases should be reviewed
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.
Test.assertEquals(actual, expected, msg)
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.