You don't say the language you're using, and also note that's the title of the tests, not the input value.

void main() {
  test("add", () { <- test title
    expect(duplicateCount(""), equals(0));
                          ^
                       input value of that test   

Please read this: https://docs.codewars.com/training/troubleshooting#print-input

Dart Completions 970

Not a kata issue.