diff --git a/src/test/java/org/apache/commons/text/StringSubstitutor_Test.java b/src/test/java/org/apache/commons/text/StringSubstitutor_Test.java
new file mode 100644
index 0000000000..bf5a8a3a96
--- /dev/null
+++ b/src/test/java/org/apache/commons/text/StringSubstitutor_Test.java
@@ -0,0 +1,71 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.commons.text;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNull;
+
+import java.util.HashMap;
+import java.util.Map;
+
+import org.junit.jupiter.api.Test;
+
+public class StringSubstitutor_TestPK {
+
+    //test for edge case Null value
+
+    @Test
+    void testReplace_NullInput() {
+        StringSubstitutor substitutor = new StringSubstitutor();
+        assertNull(substitutor.replace((String) null), "Expected null when input is null");
+    }
+    
+    // Edge case testing by testing empty string
+    @Test
+    void testReplace_EmptyString() {
+        StringSubstitutor substitutor = new StringSubstitutor();
+        assertEquals("", substitutor.replace(""), "Expected empty string to remain empty");
+    }
+    // No placeholder test
+     @Test
+    void testReplace_NoPlaceholders() {
+        StringSubstitutor substitutor = new StringSubstitutor();
+        String input = "Hello, World!";
+        assertEquals(input, substitutor.replace(input), "Expected the same string when no placeholders exist");
+    }
+    //test valid substitution
+    @Test
+    void testReplace_ValidSubstitution() {
+        Map<String, String> values = new HashMap<>();
+        values.put("name", "Jacob");
+        StringSubstitutor substitutor = new StringSubstitutor(values);
+
+        String input = "Hello, ${name}!";
+        String expected = "Hello, Jacob!";
+        assertEquals(expected, substitutor.replace(input), "Expected placeholder to be replaced");
+    }
+    @Test
+    void testReplace_UnresolvedPlaceholder() {
+        Map<String, String> values = new HashMap<>();
+        values.put("name", "Alice");
+        StringSubstitutor substitutor = new StringSubstitutor(values);
+
+        String input = "Hello, ${unknown}!";
+        String expected = "Hello, ${unknown}!";
+        assertEquals(expected, substitutor.replace(input), "Expected unresolved placeholder to remain unchanged");
+    }
+}
diff --git a/src/test/java/org/apache/commons/text/WordUtils_Test.java b/src/test/java/org/apache/commons/text/WordUtils_Test.java
new file mode 100644
index 0000000000..cd3f813baf
--- /dev/null
+++ b/src/test/java/org/apache/commons/text/WordUtils_Test.java
@@ -0,0 +1,200 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.commons.text;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import org.apache.commons.lang3.StringUtils;
+
+import org.junit.jupiter.api.Test;
+
+public class WordUtils_TestPk {
+
+ 
+
+
+   //Testing empty string and no deliminitor
+    @Test
+    public void testCapitalizePartitionEmptyString() {
+        //setup
+
+       String str="";
+       char[] delimiters ={};
+       
+       //test
+       String result= WordUtils.capitalize(str, delimiters);
+
+       //verify
+
+        assertEquals("", result);
+    }
+  
+    // testing single lower case string
+    @Test 
+    public void testCapitalizePartitionLowerCaseString(){
+        //set up
+        String str= "hello";
+        char[] delimiters ={};
+
+        //test
+        String result= WordUtils.capitalize(str, delimiters);
+
+        //verify
+
+        assertEquals("Hello", result);
+    }
+      //testing multiple lower case string with no deliminator
+    @Test 
+    public void testCapitalizePartitionMultipleLowerCaseString(){
+        //set up
+        String str= "hello world";
+        char[] delimiters ={};
+
+        //test
+        String result= WordUtils.capitalize(str, delimiters);
+
+        //verify
+
+        assertEquals("Hello world", result);
+    }
+     // multiple lower case string with a space deliminiter
+    @Test 
+    public void testCapitalizePartitionMultipleLowerCaseStringWithDeli(){
+        //set up
+        String str= "hello world";
+        char[] delimiters ={' '};
+
+        //test
+        String result= WordUtils.capitalize(str, delimiters);
+
+        //verify
+
+        assertEquals("Hello World", result);
+    }
+       // words already capitalized with a space deliminiter
+       @Test 
+       public void testCapitalizePartitionUpperCaseStringWithDeli(){
+           //set up
+           String str= "Hello World";
+           char[] delimiters ={' '};
+   
+           //test
+           String result= WordUtils.capitalize(str, delimiters);
+   
+           //verify
+   
+           assertEquals("Hello World", result);
+       }
+       // words all capitalized with a multiple deliminiter
+       @Test 
+       public void testCapitalizePartitionStringWithMultipleDeli(){
+           //set up
+           String str= "hello-world";
+           char[] delimiters ={' ','-'};
+   
+           //test
+           String result= WordUtils.capitalize(str, delimiters);
+   
+           //verify
+   
+           assertEquals("Hello-World", result);
+       }
+       // words with special character as deliminiter
+       @Test 
+       public void testCapitalizePartitionWithSpecialDeli(){
+           //set up
+           String str= "hello@world";
+           char[] delimiters ={' '};
+   
+           //test
+           String result= WordUtils.capitalize(str, delimiters);
+   
+           //verify
+   
+           assertEquals("Hello@world", result);
+       }
+       // words already capitalized with a space deliminiter
+       @Test 
+       public void testCapitalizePartitionAllUpperCaseWithDeli(){
+           //set up
+           String str= "HELLO WORLD";
+           char[] delimiters ={' '};
+   
+           //test
+           String result= WordUtils.capitalize(str, delimiters);
+   
+           //verify
+   
+           assertEquals("HELLO WORLD", result);
+       }
+       // words already capitalized with a space deliminiter
+       @Test 
+       public void testCapitalizePartitionStringWithNumbersWithDeli(){
+           //set up
+           String str= "Hello World";
+           char[] delimiters ={' '};
+   
+           //test
+           String result= WordUtils.capitalize(str, delimiters);
+   
+           //verify
+   
+           assertEquals("Hello World", result);
+       }
+       // words with a space deliminiter at the start
+       @Test 
+       public void testCapitalizePartitionWithDeliAtStart(){
+           //set up
+           String str= " hello";
+           char[] delimiters ={' '};
+   
+           //test
+           String result= WordUtils.capitalize(str, delimiters);
+   
+           //verify
+   
+           assertEquals(" Hello", result);
+       }
+       // words with a space deliminiter at the end
+       @Test 
+       public void testCapitalizePartitionWithDeliAtEnd(){
+           //set up
+           String str= "hello ";
+           char[] delimiters ={' '};
+   
+           //test
+           String result= WordUtils.capitalize(str, delimiters);
+   
+           //verify
+   
+           assertEquals("Hello ", result);
+       }
+       // lower case word only first letter is capital with no deliminiter
+       @Test 
+       public void testCapitalizePartitionNoDeliminiters(){
+           //set up
+           String str= "hello world";
+           char[] delimiters ={};
+   
+           //test
+           String result= WordUtils.capitalize(str, delimiters);
+   
+           //verify
+   
+           assertEquals("Hello world", result);
+       }
+}