diff --git a/java-collections-maps-3/src/test/java/com/baeldung/map/invert/InvertHashMapUnitTest.java b/java-collections-maps-3/src/test/java/com/baeldung/map/invert/InvertHashMapUnitTest.java
index 5759cc76d6..6870cdef23 100644
--- a/java-collections-maps-3/src/test/java/com/baeldung/map/invert/InvertHashMapUnitTest.java
+++ b/java-collections-maps-3/src/test/java/com/baeldung/map/invert/InvertHashMapUnitTest.java
@@ -1,5 +1,6 @@
 package com.baeldung.map.invert;
 
+import static org.junit.Assert.assertNotEquals;
 import static org.junit.Assert.assertNotNull;
 import static org.junit.Assert.assertTrue;
 import static org.junit.jupiter.api.Assertions.assertEquals;
@@ -8,7 +9,7 @@ import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 
-import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.TestInstance;
 
@@ -17,44 +18,55 @@ public class InvertHashMapUnitTest {
 
     Map<String, Integer> sourceMap;
 
-    @BeforeAll
+    @BeforeEach
     void setup() {
         sourceMap = new HashMap<>();
         sourceMap.put("Sunday", 0);
         sourceMap.put("Monday", 1);
+        sourceMap.put("Tuesday", 2);
+        sourceMap.put("Wednesday", 3);
+        sourceMap.put("Thursday", 4);
+        sourceMap.put("Friday", 5);
+        sourceMap.put("Saturday", 6);
     }
 
     @Test
-    void test1_invertMapUsingForLoop() {
+    void givenSourceMap_whenUsingForLoop_returnsInvertedMap() {
         Map<Integer, String> inversedMap = InvertHashMapExample.invertMapUsingForLoop(sourceMap);
+        
         assertNotNull(inversedMap);
-        assertEquals(inversedMap.size(), 2);
+        assertEquals(sourceMap.size(), inversedMap.size());
         assertEquals("Monday", inversedMap.get(1));
     }
 
     @Test
-    void test2_invertMapUsingStreams() {
+    void givenSourceMap_whenUsingStreams_returnsInvertedMap() {
         Map<Integer, String> inversedMap = InvertHashMapExample.invertMapUsingStreams(sourceMap);
+        
         assertNotNull(inversedMap);
-        assertEquals(inversedMap.size(), 2);
+        assertEquals(sourceMap.size(), inversedMap.size());
         assertEquals("Monday", inversedMap.get(1));
     }
 
     @Test
-    void test3_invertMapUsingMapper() {
+    void givenSourceMap_whenUsingMapper_returnsInvertedMap() {
         Map<Integer, String> inversedMap = InvertHashMapExample.invertMapUsingMapper(sourceMap);
+        
         assertNotNull(inversedMap);
-        assertEquals(inversedMap.size(), 2);
+        assertEquals(sourceMap.size(), inversedMap.size());
         assertEquals("Monday", inversedMap.get(1));
     }
 
     @Test
-    void test4_invertMapUsingGroupingBy() {
-        sourceMap.put("monday", 1);
+    void givenSourceMapWithDuplicateValues_whenUsingGroupBy_returnsInvertedMap() {
+        sourceMap.put("MONDAY", 1);
         Map<Integer, List<String>> inversedMap = InvertHashMapExample.invertMapUsingGroupingBy(sourceMap);
+        
         assertNotNull(inversedMap);
-        assertEquals(inversedMap.size(), 2);
-        assertTrue(inversedMap.get(1) instanceof List);
+        assertNotEquals(sourceMap.size(), inversedMap.size()); // duplicate keys are merged now
+        assertEquals(2, inversedMap.get(1).size());
+        assertTrue(inversedMap.get(1).contains("Monday"));
+        assertTrue(inversedMap.get(1).contains("MONDAY"));
     }
 
 }