diff --git a/libraries-6/src/test/java/com/baeldung/apache/commons/CollectionsUnitTest.java b/libraries-6/src/test/java/com/baeldung/apache/commons/CollectionsUnitTest.java
new file mode 100644
index 0000000000..aa5e09b443
--- /dev/null
+++ b/libraries-6/src/test/java/com/baeldung/apache/commons/CollectionsUnitTest.java
@@ -0,0 +1,109 @@
+package com.baeldung.apache.commons;
+
+import static org.junit.Assert.assertArrayEquals;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+
+import org.apache.commons.collections4.BidiMap;
+import org.apache.commons.collections4.MultiValuedMap;
+import org.apache.commons.collections4.bidimap.TreeBidiMap;
+import org.apache.commons.collections4.map.MultiKeyMap;
+import org.apache.commons.collections4.multimap.ArrayListValuedHashMap;
+import org.junit.Test;
+
+public class CollectionsUnitTest {
+    private final static BidiMap<Integer, String> daysOfWeek = new TreeBidiMap<Integer, String>();
+    private final static MultiValuedMap<String, String> groceryCart = new ArrayListValuedHashMap<>();
+    private final static MultiKeyMap<String, String> days = new MultiKeyMap<String, String>();
+    private final static MultiKeyMap<String, String> cityCoordinates = new MultiKeyMap<String, String>();
+
+    static {
+        daysOfWeek.put(1, "Monday");
+        daysOfWeek.put(2, "Tuesday");
+        daysOfWeek.put(3, "Wednesday");
+        daysOfWeek.put(4, "Thursday");
+        daysOfWeek.put(5, "Friday");
+        daysOfWeek.put(6, "Saturday");
+        daysOfWeek.put(7, "Sunday");
+
+        groceryCart.put("Fruits", "Apple");
+        groceryCart.put("Fruits", "Grapes");
+        groceryCart.put("Fruits", "Strawberries");
+        groceryCart.put("Vegetables", "Spinach");
+        groceryCart.put("Vegetables", "Cabbage");
+
+        days.put("Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Weekday");
+        days.put("Saturday", "Sunday", "Weekend");
+
+        cityCoordinates.put("40.7128° N", "74.0060° W", "New York");
+        cityCoordinates.put("48.8566° N", "2.3522° E", "Paris");
+        cityCoordinates.put("19.0760° N", "72.8777° E", "Mumbai");
+
+    }
+
+    @Test
+    public void givenBidiMap_whenValue_thenKeyReturned() {
+        assertEquals(Integer.valueOf(7), daysOfWeek.inverseBidiMap()
+            .get("Sunday"));
+    }
+
+    @Test
+    public void givenBidiMap_whenKey_thenValueReturned() {
+        assertEquals("Tuesday", daysOfWeek.get(2));
+    }
+
+    @Test
+    public void givenMultiValuedMap_whenFruitsFetched_thenFruitsReturned() {
+
+        List<String> fruits = Arrays.asList("Apple", "Grapes", "Strawberries");
+        assertEquals(fruits, groceryCart.get("Fruits"));
+    }
+
+    @Test
+    public void givenMultiValuedMap_whenVeggiesFetched_thenVeggiesReturned() {
+        List<String> veggies = Arrays.asList("Spinach", "Cabbage");
+        assertEquals(veggies, groceryCart.get("Vegetables"));
+    }
+
+    @Test
+    public void givenMultiValuedMap_whenFuitsRemoved_thenVeggiesPreserved() {
+
+        assertEquals(5, groceryCart.size());
+
+        groceryCart.remove("Fruits");
+        assertEquals(2, groceryCart.size());
+    }
+
+    @Test
+    public void givenDaysMultiKeyMap_whenFetched_thenOK() {
+        assertFalse(days.get("Saturday", "Sunday")
+            .equals("Weekday"));
+    }
+
+    @Test
+    public void givenCoordinatesMultiKeyMap_whenQueried_thenOK() {
+        List<String> expectedLongitudes = Arrays.asList("72.8777° E", "2.3522° E", "74.0060° W");
+        List<String> longitudes = new ArrayList<>();
+
+        cityCoordinates.forEach((key, value) -> {
+            longitudes.add(key.getKey(1));
+        });
+
+        assertArrayEquals(expectedLongitudes.toArray(), longitudes.toArray());
+
+        List<String> expectedCities = Arrays.asList("Mumbai", "Paris", "New York");
+        List<String> cities = new ArrayList<>();
+
+        cityCoordinates.forEach((key, value) -> {
+            cities.add(value);
+        });
+
+        assertArrayEquals(expectedCities.toArray(), cities.toArray());
+
+    }
+
+}
\ No newline at end of file
diff --git a/libraries-6/src/test/java/com/baeldung/guava/GuavaUnitTest.java b/libraries-6/src/test/java/com/baeldung/guava/GuavaUnitTest.java
new file mode 100644
index 0000000000..13a676e709
--- /dev/null
+++ b/libraries-6/src/test/java/com/baeldung/guava/GuavaUnitTest.java
@@ -0,0 +1,118 @@
+package com.baeldung.guava;
+
+import static org.junit.Assert.assertArrayEquals;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+
+import java.util.Arrays;
+import java.util.List;
+
+import org.junit.Test;
+
+import com.google.common.collect.ArrayListMultimap;
+import com.google.common.collect.BiMap;
+import com.google.common.collect.HashBasedTable;
+import com.google.common.collect.HashBiMap;
+import com.google.common.collect.Multimap;
+import com.google.common.collect.Table;
+
+public class GuavaUnitTest {
+    private final static BiMap<Integer, String> daysOfWeek = HashBiMap.create();
+    private final static Multimap<String, String> groceryCart = ArrayListMultimap.create();
+    private final static Table<String, String, String> cityCoordinates = HashBasedTable.create();
+    private final static Table<String, String, String> movies = HashBasedTable.create();
+
+    static {
+        daysOfWeek.put(1, "Monday");
+        daysOfWeek.put(2, "Tuesday");
+        daysOfWeek.put(3, "Wednesday");
+        daysOfWeek.put(4, "Thursday");
+        daysOfWeek.put(5, "Friday");
+        daysOfWeek.put(6, "Saturday");
+        daysOfWeek.put(7, "Sunday");
+
+        groceryCart.put("Fruits", "Apple");
+        groceryCart.put("Fruits", "Grapes");
+        groceryCart.put("Fruits", "Strawberries");
+        groceryCart.put("Vegetables", "Spinach");
+        groceryCart.put("Vegetables", "Cabbage");
+
+        cityCoordinates.put("40.7128° N", "74.0060° W", "New York");
+        cityCoordinates.put("48.8566° N", "2.3522° E", "Paris");
+        cityCoordinates.put("19.0760° N", "72.8777° E", "Mumbai");
+
+        movies.put("Tom Hanks", "Meg Ryan", "You've Got Mail");
+        movies.put("Tom Hanks", "Catherine Zeta-Jones", "The Terminal");
+        movies.put("Bradley Cooper", "Lady Gaga", "A Star is Born");
+        movies.put("Keenu Reaves", "Sandra Bullock", "Speed");
+        movies.put("Tom Hanks", "Sandra Bullock", "Extremely Loud & Incredibly Close");
+    }
+
+    @Test
+    public void givenBiMap_whenValue_thenKeyReturned() {
+        assertEquals(Integer.valueOf(7), daysOfWeek.inverse()
+            .get("Sunday"));
+    }
+
+    @Test
+    public void givenBiMap_whenKey_thenValueReturned() {
+        assertEquals("Tuesday", daysOfWeek.get(2));
+    }
+
+    @Test
+    public void givenMultiValuedMap_whenFruitsFetched_thenFruitsReturned() {
+
+        List<String> fruits = Arrays.asList("Apple", "Grapes", "Strawberries");
+        assertEquals(fruits, groceryCart.get("Fruits"));
+    }
+
+    @Test
+    public void givenMultiValuedMap_whenVeggiesFetched_thenVeggiesReturned() {
+        List<String> veggies = Arrays.asList("Spinach", "Cabbage");
+        assertEquals(veggies, groceryCart.get("Vegetables"));
+    }
+
+    @Test
+    public void givenMultiValuedMap_whenFuitsRemoved_thenVeggiesPreserved() {
+
+        assertEquals(5, groceryCart.size());
+
+        groceryCart.remove("Fruits", "Apple");
+        assertEquals(4, groceryCart.size());
+
+        groceryCart.removeAll("Fruits");
+        assertEquals(2, groceryCart.size());
+    }
+
+    @Test
+    public void givenCoordinatesTable_whenFetched_thenOK() {
+
+        List<String> expectedLongitudes = Arrays.asList("74.0060° W", "2.3522° E", "72.8777° E");
+
+        assertArrayEquals(expectedLongitudes.toArray(), cityCoordinates.columnKeySet()
+            .toArray());
+
+        List<String> expectedCities = Arrays.asList("New York", "Paris", "Mumbai");
+
+        assertArrayEquals(expectedCities.toArray(), cityCoordinates.values()
+            .toArray());
+
+        assertTrue(cityCoordinates.rowKeySet()
+            .contains("48.8566° N"));
+
+    }
+
+    @Test
+    public void givenMoviesTable_whenFetched_thenOK() {
+        assertEquals(3, movies.row("Tom Hanks")
+            .size());
+
+        assertEquals(2, movies.column("Sandra Bullock")
+            .size());
+
+        assertEquals("A Star is Born", movies.get("Bradley Cooper", "Lady Gaga"));
+
+        assertTrue(movies.containsValue("Speed"));
+
+    }
+}
\ No newline at end of file