diff --git a/pgpainless-core/src/test/java/org/pgpainless/util/CollectionUtilsTest.java b/pgpainless-core/src/test/java/org/pgpainless/util/CollectionUtilsTest.java
new file mode 100644
index 00000000..2bfe6cb1
--- /dev/null
+++ b/pgpainless-core/src/test/java/org/pgpainless/util/CollectionUtilsTest.java
@@ -0,0 +1,112 @@
+// SPDX-FileCopyrightText: 2022 Paul Schaub <vanitasvitae@fsfe.org>
+//
+// SPDX-License-Identifier: Apache-2.0
+
+package org.pgpainless.util;
+
+import static org.junit.jupiter.api.Assertions.assertArrayEquals;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.Iterator;
+import java.util.List;
+
+import org.junit.jupiter.api.Test;
+
+public class CollectionUtilsTest {
+
+    @Test
+    public void testConcat() {
+        String a = "A";
+        String[] bc = new String[] {"B", "C"};
+
+        String[] abc = CollectionUtils.concat(a, bc);
+        assertArrayEquals(new String[] {"A", "B", "C"}, abc);
+    }
+
+    @Test
+    public void testConcatWithEmptyArray() {
+        String a = "A";
+        String[] empty = new String[0];
+
+        String[] concat = CollectionUtils.concat(a, empty);
+        assertArrayEquals(new String[] {"A"}, concat);
+    }
+
+    @Test
+    public void iteratorToListTest() {
+        List<String> list = Arrays.asList("A", "B", "C");
+        Iterator<String> iterator = list.iterator();
+
+        List<String> listFromIterator = CollectionUtils.iteratorToList(iterator);
+        assertEquals(list, listFromIterator);
+    }
+
+    @Test
+    public void iteratorToList_emptyIteratorTest() {
+        Iterator<String> iterator = Collections.emptyIterator();
+
+        List<String> listFromIterator = CollectionUtils.iteratorToList(iterator);
+        assertTrue(listFromIterator.isEmpty());
+    }
+
+    @Test
+    public void containsTest() {
+        String[] abc = new String[] {"A", "B", "C"};
+
+        assertTrue(CollectionUtils.contains(abc, "A"));
+        assertTrue(CollectionUtils.contains(abc, "B"));
+        assertTrue(CollectionUtils.contains(abc, "C"));
+        assertFalse(CollectionUtils.contains(abc, "D"));
+    }
+
+    @Test
+    public void contains_emptyTest() {
+        String[] empty = new String[0];
+
+        assertFalse(CollectionUtils.contains(empty, "A"));
+    }
+
+    @Test
+    public void addAllTest() {
+        List<String> list = new ArrayList<>();
+        list.add("A");
+        list.add("B");
+
+        List<String> other = new ArrayList<>();
+        other.add("C");
+        other.add("D");
+        Iterator<String> iterator = other.iterator();
+
+        CollectionUtils.addAll(iterator, list);
+
+        assertEquals(Arrays.asList("A", "B", "C", "D"), list);
+    }
+
+    @Test
+    public void addAllEmptyListTest() {
+        List<String> empty = new ArrayList<>();
+
+        List<String> other = Arrays.asList("A", "B", "C");
+        Iterator<String> iterator = other.iterator();
+
+        CollectionUtils.addAll(iterator, empty);
+        assertEquals(Arrays.asList("A", "B", "C"), empty);
+    }
+
+    @Test
+    public void addAllEmptyIterator() {
+        List<String> list = new ArrayList<>();
+        list.add("A");
+        list.add("B");
+
+        Iterator<String> iterator = Collections.emptyIterator();
+
+        CollectionUtils.addAll(iterator, list);
+        assertEquals(Arrays.asList("A", "B"), list);
+    }
+}