chore(tests): add some edge tests

Author: sozelfist

src/string/rabin_karp.rs

@@ -109,7 +109,9 @@ mod tests {
         target_is_multiple_patterns: ("abcabcabc", "abc", vec![0, 3, 6]),
         empty_text: ("", "abc", vec![]),
         empty_pattern: ("abc", "", vec![]),
+        empty_text_and_pattern: ("", "", vec![]),
         pattern_larger_than_text: ("abc", "abcd", vec![]),
+        large_text_small_pattern: (&("a".repeat(1000) + "b"), "b", vec![1000]),
         single_char_match: ("a", "a", vec![0]),
         single_char_no_match: ("a", "b", vec![]),
         large_pattern_no_match: ("abc", "defghi", vec![]),