Name of function 'sum_two_smallest_numbers' made me suspicious (what if there is negative in array, or less 2 elements), re-reading the description, ok ok :)

This assumes all numbers are positive integers

Correct: "No floats or non-positive integers will be passed."

and that the provided list of numbers has two items.

Correct too: "... given an array of minimum 4 positive integers"

This assumes all numbers are positive integers, and that the provided list of numbers has two items.