There is no such test, but you solved it already. What was the problem?

btw, you have an off-by-one allocation error there: you need 5 bytes to store "word", don't forget the nul-terminator that marks the end of the string: { 'w', 'o', 'r', 'd', '\0' }

yeah, it's complicated to provide better feedback because in C you usually cannot check whether a given pointer is valid or not. so the tests will compare the random pointers in words_array and it's likely to lead to a segfault.

that being said, i just updated the tests to be more user-friendly: words_array will be initially filled with NULL pointers; and the tests will handle those NULLs safely for both comparison and composing the assertion message. your code no longer crashes now.

you have an array of pointers, words_array. it contains as many elements as there are words in the string, but initially (when words_to_array() is called), it does not contain anything meaningful; you have to fill it with strings allocated on the heap (i.e. with malloc/calloc/strdup())

you realized your mistake but forgot to close your question afterwards

OP solved the kata

Could you explain how you got 1201, because 2110 is the correct answer. You should make it so the digits are sorted in descending order (essentially a greater number comes before a lesser number, and we can see that your answer is incorrect as 1 comes before 2, but 2 is a greater digit