Add simple test for StreamIterator (#490)

* Add simple test for StreamIterator

* Fix build

---------

Co-authored-by: Gary Gregory <garydgregory@users.noreply.github.com>

Author: labkey-adam

src/test/java/org/apache/commons/io/StreamIteratorTest.java

@@ -0,0 +1,43 @@
+/*
+ * 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;
+
+import org.junit.jupiter.api.Test;
+
+import java.util.Iterator;
+import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.stream.Stream;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+public class StreamIteratorTest {
+    @Test
+    public void testStreamIterator() {
+        final AtomicBoolean closed = new AtomicBoolean();
+        final Iterator<Integer> iter = StreamIterator.iterator(Stream.of(1, 2, 3).onClose(() -> closed.set(true)));
+        int sum = 0;
+
+        while (iter.hasNext()) {
+            sum += iter.next();
+        }
+
+        assertEquals(6, sum);
+        assertTrue(closed.get());
+    }
+}