Design a C function that shortens a string to 8 characters

#include "base.h"
#include "string.h"
/*
Design a function that shortens a string to 8 characters.
*/
// String -> String    
String truncate(String string);
void truncate_test() {
    check_expect_s(truncate("1234567891011"), "12345678");      // line 19
    check_expect_s(truncate("123"), "123");                             // line 20
    check_expect_s(truncate("12345678"), "12345678");           // line 21
}
// Returns the original string or shortens it to the first 8 characters.
String truncate(String string) {
    if (s_length(string) <= 8) {
        return(string);
    } else {
        return(s_sub(string, 0,8));
    }
        return 0;
}
int main(void) {
    truncate_test();
    return 0;
    }