props does not necessarily have a fixed length of 2, your code fails to handle cases like a.b.c

Sounds like input mutation, given the number of people who have passed it, and the fact that when you test it by itself it works fine.

Please post the message of the none passing test cases.

Too few:

• code and war can't be merged to codewars because there are not enough characters in the parts.

To many (extra):

• code and warsx can't be merged to codewars because there is an extra x that isn't used.

All characters of the parts should be used and they should form the entire target to be considered a valid merge.

Does that answer your question?