diff --git a/exercises/custom-set/.meta/version b/exercises/custom-set/.meta/version
new file mode 100644
index 000000000..7dea76edb
--- /dev/null
+++ b/exercises/custom-set/.meta/version
@@ -0,0 +1 @@
+1.0.1
diff --git a/exercises/custom-set/src/test/java/CustomSetTest.java b/exercises/custom-set/src/test/java/CustomSetTest.java
index a28287d97..3dbb7fe01 100644
--- a/exercises/custom-set/src/test/java/CustomSetTest.java
+++ b/exercises/custom-set/src/test/java/CustomSetTest.java
@@ -1,264 +1,181 @@
+import org.junit.Ignore;
+import org.junit.Test;
 
 import java.util.Arrays;
 import java.util.Collections;
-import static org.junit.Assert.assertFalse;
-import static org.junit.Assert.assertNotNull;
-import static org.junit.Assert.assertTrue;
-import org.junit.Test;
-import org.junit.Ignore;
+
+import static org.junit.Assert.*;
 
 public class CustomSetTest {
 
     @Test
     public void setsWithNoElementsAreEmpty() {
-        final boolean actual
-                = new CustomSet<>(Collections.emptyList())
-                        .isEmpty();
-        assertTrue(actual);
+        CustomSet<Integer> customSet = new CustomSet<>(Collections.emptyList());
+        assertTrue(customSet.isEmpty());
     }
 
     @Ignore("Remove to run test")
     @Test
     public void setsWithElementsAreNotEmpty() {
-        final boolean actual
-                = new CustomSet<>(Collections.singletonList(1))
-                        .isEmpty();
-
-        assertFalse(actual);
+        CustomSet<Character> customSet = new CustomSet<>(Collections.singletonList('1'));
+        assertFalse(customSet.isEmpty());
     }
 
     @Ignore("Remove to run test")
     @Test
     public void nothingIsContainedInAnEmptySet() {
-        final boolean actual
-                = new CustomSet<>(Collections.emptyList())
-                        .contains(1);
-
-        assertFalse(actual);
+        CustomSet<String> customSet = new CustomSet<>(Collections.emptyList());
+        assertFalse(customSet.contains("1"));
     }
 
     @Ignore("Remove to run test")
     @Test
     public void whenTheElementIsInTheSet() {
-        final boolean actual
-                = new CustomSet<>(Arrays.asList(1, 2, 3))
-                        .contains(1);
-
-        assertTrue(actual);
+        CustomSet<Integer> customSet = new CustomSet<>(Arrays.asList(1, 2, 3));
+        assertTrue(customSet.contains(1));
     }
 
     @Ignore("Remove to run test")
     @Test
     public void whenTheElementIsNotInTheSet() {
-        final boolean actual
-                = new CustomSet<>(Arrays.asList(1, 2, 3))
-                        .contains(4);
-
-        assertFalse(actual);
+        CustomSet<Character> customSet = new CustomSet<>(Arrays.asList('1', '2', '3'));
+        assertFalse(customSet.contains('4'));
     }
 
     @Ignore("Remove to run test")
     @Test
     public void emptySetIsASubsetOfAnotherEmptySet() {
-        final boolean actual
-                = new CustomSet<>(Collections.emptyList())
-                        .isSubset(
-                                new CustomSet<>(Collections.emptyList())
-                        );
-
-        assertTrue(actual);
+        CustomSet<String> customSet = new CustomSet<>(Collections.emptyList());
+        CustomSet<String> secondCustomSet = new CustomSet<>(Collections.emptyList());
+        assertTrue(customSet.isSubset(secondCustomSet));
     }
 
     @Ignore("Remove to run test")
     @Test
     public void emptySetIsASubsetOfNonEmptySet() {
-        final boolean actual
-                = new CustomSet<>(Collections.singletonList(1))
-                        .isSubset(
-                                new CustomSet<>(Collections.emptyList())
-                        );
-
-        assertTrue(actual);
+        CustomSet<Integer> customSet = new CustomSet<>(Collections.singletonList(1));
+        CustomSet<Integer> secondCustomSet = new CustomSet<>(Collections.emptyList());
+        assertTrue(customSet.isSubset(secondCustomSet));
     }
 
     @Ignore("Remove to run test")
     @Test
     public void nonEmptySetIsNotASubsetOfEmptySet() {
-        final boolean actual
-                = new CustomSet<>(Collections.emptyList())
-                        .isSubset(
-                                new CustomSet<>(Collections.singletonList(1))
-                        );
-
-        assertFalse(actual);
+        CustomSet<Character> customSet = new CustomSet<>(Collections.emptyList());
+        CustomSet<Character> secondCustomSet = new CustomSet<>(Collections.singletonList('1'));
+        assertFalse(customSet.isSubset(secondCustomSet));
     }
 
     @Ignore("Remove to run test")
     @Test
     public void setIsASubsetOfSetWithExactSameElements() {
-        final boolean actual
-                = new CustomSet<>(Arrays.asList(1, 2, 3))
-                        .isSubset(
-                                new CustomSet<>(Arrays.asList(1, 2, 3))
-                        );
-
-        assertTrue(actual);
+        CustomSet<String> customSet = new CustomSet<>(Arrays.asList("1", "2", "3"));
+        CustomSet<String> secondCustomSet = new CustomSet<>(Arrays.asList("1", "2", "3"));
+        assertTrue(customSet.isSubset(secondCustomSet));
     }
 
     @Ignore("Remove to run test")
     @Test
     public void setIsASubsetOfLargerSetWithSameElements() {
-        final boolean actual
-                = new CustomSet<>(Arrays.asList(4, 1, 2, 3))
-                        .isSubset(
-                                new CustomSet<>(Arrays.asList(1, 2, 3))
-                        );
-
-        assertTrue(actual);
+        CustomSet<Integer> customSet = new CustomSet<>(Arrays.asList(4, 1, 2, 3));
+        CustomSet<Integer> secondCustomSet = new CustomSet<>(Arrays.asList(1, 2, 3));
+        assertTrue(customSet.isSubset(secondCustomSet));
     }
 
     @Ignore("Remove to run test")
     @Test
     public void setIsNotASubsetOfSetThatDoesNotContainItsElements() {
-        final boolean actual
-                = new CustomSet<>(Arrays.asList(4, 1, 3))
-                        .isSubset(
-                                new CustomSet<>(Arrays.asList(1, 2, 3))
-                        );
-
-        assertFalse(actual);
+        CustomSet<Character> customSet = new CustomSet<>(Arrays.asList('4', '1', '3'));
+        CustomSet<Character> secondCustomSet = new CustomSet<>(Arrays.asList('1', '2', '3'));
+        assertFalse(customSet.isSubset(secondCustomSet));
     }
 
     @Ignore("Remove to run test")
     @Test
     public void theEmptySetIsDisjointWithItself() {
-        final boolean actual
-                = new CustomSet<>(Collections.emptyList())
-                        .isDisjoint(
-                                new CustomSet<>(Collections.emptyList())
-                        );
-
-        assertTrue(actual);
+        CustomSet<String> customSet = new CustomSet<>(Collections.emptyList());
+        CustomSet<String> secondCustomSet = new CustomSet<>(Collections.emptyList());
+        assertTrue(customSet.isDisjoint(secondCustomSet));
     }
 
     @Ignore("Remove to run test")
     @Test
     public void emptySetIsDisjointWithNonEmptySet() {
-        final boolean actual
-                = new CustomSet<>(Collections.emptyList())
-                        .isDisjoint(
-                                new CustomSet<>(Collections.singletonList(1))
-                        );
-
-        assertTrue(actual);
+        CustomSet<Integer> customSet = new CustomSet<>(Collections.emptyList());
+        CustomSet<Integer> secondCustomSet = new CustomSet<>(Collections.singletonList(1));
+        assertTrue(customSet.isDisjoint(secondCustomSet));
     }
 
     @Ignore("Remove to run test")
     @Test
     public void nonEmptySetIsDisjointWithEmptySet() {
-        final boolean actual
-                = new CustomSet<>(Collections.singletonList(1))
-                        .isDisjoint(
-                                new CustomSet<>(Collections.emptyList())
-                        );
-
-        assertTrue(actual);
+        CustomSet<Character> customSet = new CustomSet<>(Collections.singletonList('1'));
+        CustomSet<Character> secondCustomSet = new CustomSet<>(Collections.emptyList());
+        assertTrue(customSet.isDisjoint(secondCustomSet));
     }
 
     @Ignore("Remove to run test")
     @Test
     public void setsAreNotDisjointIfTheyShareAnElement() {
-        final boolean actual
-                = new CustomSet<>(Arrays.asList(1, 2))
-                        .isDisjoint(
-                                new CustomSet<>(Arrays.asList(2, 3))
-                        );
-
-        assertFalse(actual);
+        CustomSet<String> customSet = new CustomSet<>(Arrays.asList("1", "2"));
+        CustomSet<String> secondCustomSet = new CustomSet<>(Arrays.asList("2", "3"));
+        assertFalse(customSet.isDisjoint(secondCustomSet));
     }
 
     @Ignore("Remove to run test")
     @Test
     public void setsAreDisjointIfTheyShareNoElements() {
-        final boolean actual
-                = new CustomSet<>(Arrays.asList(1, 2))
-                        .isDisjoint(
-                                new CustomSet<>(Arrays.asList(3, 4))
-                        );
-
-        assertTrue(actual);
+        CustomSet<Integer> customSet = new CustomSet<>(Arrays.asList(1, 2));
+        CustomSet<Integer> secondCustomSet = new CustomSet<>(Arrays.asList(3, 4));
+        assertTrue(customSet.isDisjoint(secondCustomSet));
     }
 
     @Ignore("Remove to run test")
     @Test
     public void emptySetsAreEqual() {
-        final boolean actual
-                = new CustomSet<>(Collections.emptyList())
-                        .equals(
-                                new CustomSet<>(Collections.emptyList())
-                        );
-
-        assertTrue(actual);
+        CustomSet<Character> customSet = new CustomSet<>(Collections.emptyList());
+        CustomSet<Character> secondCustomSet = new CustomSet<>(Collections.emptyList());
+        assertTrue(customSet.equals(secondCustomSet));
     }
 
     @Ignore("Remove to run test")
     @Test
     public void emptySetIsNotEqualToNonEmptySet() {
-        final boolean actual
-                = new CustomSet<>(Collections.emptyList())
-                        .equals(
-                                new CustomSet<>(Arrays.asList(1, 2, 3))
-                        );
-
-        assertFalse(actual);
+        CustomSet<String> customSet = new CustomSet<>(Collections.emptyList());
+        CustomSet<String> secondCustomSet = new CustomSet<>(Arrays.asList("1", "2", "3"));
+        assertFalse(customSet.equals(secondCustomSet));
     }
 
     @Ignore("Remove to run test")
     @Test
     public void nonEmptySetIsNotEqualToEmptySet() {
-        final boolean actual
-                = new CustomSet<>(Arrays.asList(1, 2, 3))
-                        .equals(
-                                new CustomSet<>(Collections.emptyList())
-                        );
-
-        assertFalse(actual);
+        CustomSet<Integer> customSet = new CustomSet<>(Arrays.asList(1, 2, 3));
+        CustomSet<Integer> secondCustomSet = new CustomSet<>(Collections.emptyList());
+        assertFalse(customSet.equals(secondCustomSet));
     }
 
     @Ignore("Remove to run test")
     @Test
     public void setsWithTheSameElementsAreEqual() {
-        final boolean actual
-                = new CustomSet<>(Arrays.asList(1, 2))
-                        .equals(
-                                new CustomSet<>(Arrays.asList(2, 1))
-                        );
-
-        assertTrue(actual);
+        CustomSet<Character> customSet = new CustomSet<>(Arrays.asList('1', '2'));
+        CustomSet<Character> secondCustomSet = new CustomSet<>(Arrays.asList('2', '1'));
+        assertTrue(customSet.equals(secondCustomSet));
     }
 
     @Ignore("Remove to run test")
     @Test
     public void setsWithDifferentElementsAreNotEqual() {
-        final boolean actual
-                = new CustomSet<>(Arrays.asList(1, 2, 3))
-                        .equals(
-                                new CustomSet<>(Arrays.asList(1, 2, 4))
-                        );
-
-        assertFalse(actual);
+        CustomSet<String> customSet = new CustomSet<>(Arrays.asList("1", "2", "3"));
+        CustomSet<String> secondCustomSet = new CustomSet<>(Arrays.asList("1", "2", "4"));
+        assertFalse(customSet.equals(secondCustomSet));
     }
 
     @Ignore("Remove to run test")
     @Test
     public void addToEmptySet() {
-        final int element = 3;
-        final CustomSet<Integer> expected
-                = new CustomSet<>(
-                        Collections.unmodifiableList(Collections.singletonList(element))
-                );
-        final CustomSet<Integer> actual
-                = new CustomSet<>(Collections.emptyList());
+        int element = 3;
+        CustomSet<Integer> expected = new CustomSet<>(Collections.unmodifiableList(Collections.singletonList(element)));
+        CustomSet<Integer> actual = new CustomSet<>(Collections.emptyList());
 
         actual.add(element);
 
@@ -270,13 +187,9 @@ public void addToEmptySet() {
     @Ignore("Remove to run test")
     @Test
     public void addToNonEmptySet() {
-        final int element = 3;
-        final CustomSet<Integer> expected
-                = new CustomSet<>(
-                        Collections.unmodifiableList(Arrays.asList(1, 2, 3, 4))
-                );
-        final CustomSet<Integer> actual
-                = new CustomSet<>(Arrays.asList(1, 2, 4));
+        char element = '3';
+        CustomSet<Character> expected = new CustomSet<>(Collections.unmodifiableList(Arrays.asList('1', '2', '3', '4')));
+        CustomSet<Character> actual = new CustomSet<>(Arrays.asList('1', '2', '4'));
 
         actual.add(element);
 
@@ -288,13 +201,9 @@ public void addToNonEmptySet() {
     @Ignore("Remove to run test")
     @Test
     public void addingAnExistingElementDoesNotChangeTheSet() {
-        final int element = 3;
-        final CustomSet<Integer> expected
-                = new CustomSet<>(
-                        Collections.unmodifiableList(Arrays.asList(1, 2, 3))
-                );
-        final CustomSet<Integer> actual
-                = new CustomSet<>(Arrays.asList(1, 2, 3));
+        String element = "3";
+        CustomSet<String> expected = new CustomSet<>(Collections.unmodifiableList(Arrays.asList("1", "2", "3")));
+        CustomSet<String> actual = new CustomSet<>(Arrays.asList("1", "2", "3"));
 
         actual.add(element);
 
@@ -305,11 +214,8 @@ public void addingAnExistingElementDoesNotChangeTheSet() {
     @Ignore("Remove to run test")
     @Test
     public void intersectionOfTwoEmptySetsIsAnEmptySet() {
-        final CustomSet<Integer> actual
-                = new CustomSet<Integer>(Collections.emptyList())
-                        .getIntersection(
-                                new CustomSet<>(Collections.emptyList())
-                        );
+        CustomSet<Integer> actual = new CustomSet<Integer>(Collections.emptyList())
+                .getIntersection(new CustomSet<>(Collections.emptyList()));
 
         assertNotNull(actual);
         assertTrue(actual.isEmpty());
@@ -318,11 +224,8 @@ public void intersectionOfTwoEmptySetsIsAnEmptySet() {
     @Ignore("Remove to run test")
     @Test
     public void intersectionOfAnEmptySetAndNonEmptySetIsAnEmptySet() {
-        final CustomSet<Integer> actual
-                = new CustomSet<Integer>(Collections.emptyList())
-                        .getIntersection(
-                                new CustomSet<>(Arrays.asList(3, 2, 5))
-                        );
+        CustomSet<Character> actual = new CustomSet<Character>(Collections.emptyList())
+                .getIntersection(new CustomSet<>(Arrays.asList('3', '2', '5')));
 
         assertNotNull(actual);
         assertTrue(actual.isEmpty());
@@ -331,11 +234,8 @@ public void intersectionOfAnEmptySetAndNonEmptySetIsAnEmptySet() {
     @Ignore("Remove to run test")
     @Test
     public void intersectionOfANonEmptySetAndAnEmptySetIsAnEmptySet() {
-        final CustomSet<Integer> actual
-                = new CustomSet<>(Arrays.asList(1, 2, 3, 4))
-                        .getIntersection(
-                                new CustomSet<>(Collections.emptyList())
-                        );
+        CustomSet<String> actual = new CustomSet<>(Arrays.asList("1", "2", "3", "4"))
+                .getIntersection(new CustomSet<>(Collections.emptyList()));
 
         assertNotNull(actual);
         assertTrue(actual.isEmpty());
@@ -345,11 +245,8 @@ public void intersectionOfANonEmptySetAndAnEmptySetIsAnEmptySet() {
     @Ignore("Remove to run test")
     @Test
     public void intersectionOfTwoSetsWithNoSharedElementsIsAnEmptySet() {
-        final CustomSet<Integer> actual
-                = new CustomSet<>(Arrays.asList(1, 2, 3))
-                        .getIntersection(
-                                new CustomSet<>(Arrays.asList(4, 5, 6))
-                        );
+        CustomSet<Integer> actual = new CustomSet<>(Arrays.asList(1, 2, 3))
+                .getIntersection(new CustomSet<>(Arrays.asList(4, 5, 6)));
 
         assertNotNull(actual);
         assertTrue(actual.isEmpty());
@@ -358,15 +255,9 @@ public void intersectionOfTwoSetsWithNoSharedElementsIsAnEmptySet() {
     @Ignore("Remove to run test")
     @Test
     public void intersectionOfTwoSetsWithSharedElementsIsASetOfTheSharedElements() {
-        final CustomSet<Integer> expected
-                = new CustomSet<>(
-                        Collections.unmodifiableList(Arrays.asList(2, 3))
-                );
-        final CustomSet<Integer> actual
-                = new CustomSet<>(Arrays.asList(1, 2, 3, 4))
-                        .getIntersection(
-                                new CustomSet<>(Arrays.asList(3, 2, 5))
-                        );
+        CustomSet<Character> expected = new CustomSet<>(Collections.unmodifiableList(Arrays.asList('2', '3')));
+        CustomSet<Character> actual = new CustomSet<>(Arrays.asList('1', '2', '3', '4'))
+                .getIntersection(new CustomSet<>(Arrays.asList('3', '2', '5')));
 
         assertNotNull(actual);
         assertFalse(actual.isEmpty());
@@ -376,11 +267,8 @@ public void intersectionOfTwoSetsWithSharedElementsIsASetOfTheSharedElements() {
     @Ignore("Remove to run test")
     @Test
     public void differenceOfTwoEmptySetsIsAnEmptySet() {
-        final CustomSet<Integer> actual
-                = new CustomSet<Integer>(Collections.emptyList())
-                        .getDifference(
-                                new CustomSet<>(Collections.emptyList())
-                        );
+        CustomSet<String> actual = new CustomSet<String>(Collections.emptyList())
+                .getDifference(new CustomSet<>(Collections.emptyList()));
 
         assertNotNull(actual);
         assertTrue(actual.isEmpty());
@@ -389,11 +277,8 @@ public void differenceOfTwoEmptySetsIsAnEmptySet() {
     @Ignore("Remove to run test")
     @Test
     public void differenceOfAnEmptySetAndNonEmptySetIsAnEmptySet() {
-        final CustomSet<Integer> actual
-                = new CustomSet<Integer>(Collections.emptyList())
-                        .getDifference(
-                                new CustomSet<>(Arrays.asList(3, 2, 5))
-                        );
+        CustomSet<Integer> actual = new CustomSet<Integer>(Collections.emptyList())
+                .getDifference(new CustomSet<>(Arrays.asList(3, 2, 5)));
 
         assertNotNull(actual);
         assertTrue(actual.isEmpty());
@@ -402,15 +287,9 @@ public void differenceOfAnEmptySetAndNonEmptySetIsAnEmptySet() {
     @Ignore("Remove to run test")
     @Test
     public void differenceOfANonEmptySetAndAnEmptySetIsTheNonEmptySet() {
-        final CustomSet<Integer> expected
-                = new CustomSet<>(
-                        Collections.unmodifiableList(Arrays.asList(1, 2, 3, 4))
-                );
-        final CustomSet<Integer> actual
-                = new CustomSet<>(Arrays.asList(1, 2, 3, 4))
-                        .getDifference(
-                                new CustomSet<>(Collections.emptyList())
-                        );
+        CustomSet<Character> expected = new CustomSet<>(Collections.unmodifiableList(Arrays.asList('1', '2', '3', '4')));
+        CustomSet<Character> actual = new CustomSet<>(Arrays.asList('1', '2', '3', '4'))
+                .getDifference(new CustomSet<>(Collections.emptyList()));
 
         assertNotNull(actual);
         assertFalse(actual.isEmpty());
@@ -420,15 +299,9 @@ public void differenceOfANonEmptySetAndAnEmptySetIsTheNonEmptySet() {
     @Ignore("Remove to run test")
     @Test
     public void differenceOfTwoNonEmptySetsIsASetOfElementsThatAreOnlyInTheFirstSet() {
-        final CustomSet<Integer> expected
-                = new CustomSet<>(
-                        Collections.unmodifiableList(Arrays.asList(1, 3))
-                );
-        final CustomSet<Integer> actual
-                = new CustomSet<>(Arrays.asList(3, 2, 1))
-                        .getDifference(
-                                new CustomSet<>(Arrays.asList(2, 4))
-                        );
+        CustomSet<String> expected = new CustomSet<>(Collections.unmodifiableList(Arrays.asList("1", "3")));
+        CustomSet<String> actual = new CustomSet<>(Arrays.asList("3", "2", "1"))
+                .getDifference(new CustomSet<>(Arrays.asList("2", "4")));
 
         assertNotNull(actual);
         assertFalse(actual.isEmpty());
@@ -438,11 +311,8 @@ public void differenceOfTwoNonEmptySetsIsASetOfElementsThatAreOnlyInTheFirstSet(
     @Ignore("Remove to run test")
     @Test
     public void unionOfTwoEmptySetsIsAnEmptySet() {
-        final CustomSet<Integer> actual
-                = new CustomSet<Integer>(Collections.emptyList())
-                        .getUnion(
-                                new CustomSet<>(Collections.emptyList())
-                        );
+        CustomSet<Integer> actual = new CustomSet<Integer>(Collections.emptyList())
+                .getUnion(new CustomSet<>(Collections.emptyList()));
 
         assertNotNull(actual);
         assertTrue(actual.isEmpty());
@@ -451,15 +321,9 @@ public void unionOfTwoEmptySetsIsAnEmptySet() {
     @Ignore("Remove to run test")
     @Test
     public void unionOfAnEmptySetAndNonEmptySetIsTheNonEmptySet() {
-        final CustomSet<Integer> expected
-                = new CustomSet<>(
-                        Collections.unmodifiableList(Collections.singletonList(2))
-                );
-        final CustomSet<Integer> actual
-                = new CustomSet<Integer>(Collections.emptyList())
-                        .getUnion(
-                                new CustomSet<>(Collections.singletonList(2))
-                        );
+        CustomSet<Character> expected = new CustomSet<>(Collections.unmodifiableList(Collections.singletonList('2')));
+        CustomSet<Character> actual = new CustomSet<Character>(Collections.emptyList())
+                .getUnion(new CustomSet<>(Collections.singletonList('2')));
 
         assertNotNull(actual);
         assertFalse(actual.isEmpty());
@@ -469,15 +333,9 @@ public void unionOfAnEmptySetAndNonEmptySetIsTheNonEmptySet() {
     @Ignore("Remove to run test")
     @Test
     public void unionOfANonEmptySetAndAnEmptySetIsTheNonEmptySet() {
-        final CustomSet<Integer> expected
-                = new CustomSet<>(
-                        Collections.unmodifiableList(Arrays.asList(1, 3))
-                );
-        final CustomSet<Integer> actual
-                = new CustomSet<>(Arrays.asList(1, 3))
-                        .getUnion(
-                                new CustomSet<>(Collections.emptyList())
-                        );
+        CustomSet<String> expected = new CustomSet<>(Collections.unmodifiableList(Arrays.asList("1", "3")));
+        CustomSet<String> actual = new CustomSet<>(Arrays.asList("1", "3"))
+                .getUnion(new CustomSet<>(Collections.emptyList()));
 
         assertNotNull(actual);
         assertFalse(actual.isEmpty());
@@ -487,15 +345,9 @@ public void unionOfANonEmptySetAndAnEmptySetIsTheNonEmptySet() {
     @Ignore("Remove to run test")
     @Test
     public void unionOfTwoNonEmptySetsContainsAllUniqueElements() {
-        final CustomSet<Integer> expected
-                = new CustomSet<>(
-                        Collections.unmodifiableList(Arrays.asList(3, 2, 1))
-                );
-        final CustomSet<Integer> actual
-                = new CustomSet<>(Arrays.asList(1, 3))
-                        .getUnion(
-                                new CustomSet<>(Arrays.asList(2, 3))
-                        );
+        CustomSet<Integer> expected = new CustomSet<>(Collections.unmodifiableList(Arrays.asList(3, 2, 1)));
+        CustomSet<Integer> actual = new CustomSet<>(Arrays.asList(1, 3))
+                .getUnion(new CustomSet<>(Arrays.asList(2, 3)));
 
         assertNotNull(actual);
         assertFalse(actual.isEmpty());