To amplify the previous report in re the random tests expect the input as the result...
Try this:
public … {
return array;
}
When you Attempt, it will pass the Random tests, and it shouldn’t.

srfoster’s solution should work, but they had to do a workaround to get past the bug.

Also, the problem wording is ambiguous (politically correct for “it sucks”). The actual solution does not match the scenario - the solution sucks up much more space.

Better wording which matches the solution:
“Write a function that takes a String array and returns a String array in which each element is the contatenation of all preceding elements plus the current element.”

Wording which matches the scenario:
“Write a function that concatenates the elements of a String array.”
Then overhaul the solution and make it 8 kyu.