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diff --git a/src/test/java/org/apache/commons/io/function/IOIteratorTest.java b/src/test/java/org/apache/commons/io/function/IOIteratorTest.java
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+/*
+ * 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.io.function;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import java.io.IOException;
+import java.nio.file.Path;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Iterator;
+import java.util.List;
+
+import org.apache.commons.lang3.JavaVersion;
+import org.apache.commons.lang3.SystemUtils;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+/**
+ * Tests {@link IOIterator}.
+ */
+public class IOIteratorTest {
+
+    private IOIterator<Path> iterator;
+
+    @BeforeEach
+    public void beforeEach() {
+        iterator = IOIterator.adapt(newPathList().iterator());
+    }
+
+    private List<Path> newPathList() {
+        return Arrays.asList(TestConstants.ABS_PATH_A, TestConstants.ABS_PATH_B);
+    }
+
+    @Test
+    public void testAdapt() throws IOException {
+        assertEquals(TestConstants.ABS_PATH_A, iterator.next());
+    }
+
+    @Test
+    public void testAsIterator() {
+        final Iterator<Path> asIterator = iterator.asIterator();
+        assertTrue(asIterator.hasNext());
+        assertEquals(TestConstants.ABS_PATH_A, asIterator.next());
+        assertThrows(UnsupportedOperationException.class, asIterator::remove);
+    }
+
+    @Test
+    public void testForEachRemaining() throws IOException {
+        final List<Path> list = new ArrayList<>();
+        iterator.forEachRemaining(p -> list.add(p.toRealPath()));
+        assertFalse(iterator.hasNext());
+        assertEquals(newPathList(), list);
+    }
+
+    @Test
+    public void testHasNext() throws IOException {
+        assertTrue(iterator.hasNext());
+        iterator.forEachRemaining(Path::toRealPath);
+        assertFalse(iterator.hasNext());
+    }
+
+    @Test
+    public void testNext() throws IOException {
+        assertEquals(TestConstants.ABS_PATH_A, iterator.next());
+    }
+
+    @Test
+    public void testRemove() throws IOException {
+        final Class<? extends Exception> exClass = SystemUtils.isJavaVersionAtMost(JavaVersion.JAVA_1_8) ? IllegalStateException.class
+            : UnsupportedOperationException.class;
+        assertThrows(exClass, iterator::remove);
+        assertThrows(exClass, iterator::remove);
+        iterator.next();
+        assertThrows(UnsupportedOperationException.class, iterator::remove);
+        assertThrows(UnsupportedOperationException.class, iterator::remove);
+    }
+
+}