If the idea is to make sure we check for invalid input, you could be a lot more evil and include fixed texts for 02/30/YEAR, 09/31/YEAR, or even 02/29/2001 if you're feeling particularly devilish. Most solutions I have seen so far would have failed those.

Right now the test cases are in an odd in-between zone: they are enough to annoy the warriors slightly and stop us from finishing the kata on autopilot, but they do not truly put our answers to the test.

Nice kata. The test cases are not good enough though. My solution produced the output 1806 (expected 1807) for input age("10/09/2104","10/09/3911"), but I could still push it through in the next submission. Also, it would be good to mention what needs to be done about leap years.

Might explicitly put in the description that rounding down is necessary.

You're right indeed. It reminds me that getMonth and getMonth() is definitely not the same thing. I made this test an example test case as well. Thanks.

Sorry about that, the right format is definitely 'mm/dd/yyyy'. Thx

Mistake in one of the tests:
Error : birthday= 06/09/3051 and enddate= 04/23/4208 -> result should be 1157 and not 1156

Description says: The entries must have this format : "mm/dd/yyyy" and one of the tests says: Should return -1, One of your date doesn't have the good format 'DD/MM/YYYY'

Thanks for the comment. I made more precise error messages. Hope it'll help

you're right. I added random test cases and corrected the examples.

thanks for commenting. I added random test cases and corrected the examples

Tests aren't descriptive and hard to debug.

1.your example testcase 3 and 4 have a wrong answer.
2.need some random testcase.