BAEL-5354 Add improvement to cover JDK11 solution to the repeated string problem (#11756)

core-java-modules/core-java-string-algorithms-3/src/test/java/com/baeldung/repeatedcharstring/RepeatedCharacterStringUnitTest.java

@@ -19,6 +19,18 @@ class RepeatedCharacterStringUnitTest {
     private static final String EXPECTED_STRING = "aaaaaaa";
     private static final int N = 7;
 
+    @Test
+    void givenSingleCharacterString_whenRepeat_thenStringCreated() {
+        String newString = "a".repeat(N);
+        assertEquals(EXPECTED_STRING, newString);
+    }
+
+    @Test
+    void givenMultiCharacterString_whenRepeat_thenStringCreated() {
+        String newString = "-->".repeat(5);
+        assertEquals("-->-->-->-->-->", newString);
+    }
+
     @Test
     void givenString_whenStringBuilderUsed_thenStringCreated() {
         StringBuilder builder = new StringBuilder(N);