content: /*
   * 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.kafka.common.utils;
  
  import org.junit.jupiter.api.Test;
  
  import java.util.Arrays;
  import java.util.Collections;
  
  import static org.junit.jupiter.api.Assertions.assertEquals;
  import static org.junit.jupiter.api.Assertions.assertNull;
  import static org.junit.jupiter.api.Assertions.assertThrows;
  import static org.junit.jupiter.api.Assertions.assertTrue;
  
  public class CircularIteratorTest {
  
      @Test
      public void testNullCollection() {
          assertThrows(NullPointerException.class, () -> new CircularIterator<>(null));
      }
  
      @Test
      public void testEmptyCollection() {
          assertThrows(IllegalArgumentException.class, () -> new CircularIterator<>(Collections.emptyList()));
      }
  
      @Test()
      public void testCycleCollection() {
          final CircularIterator<String> it = new CircularIterator<>(Arrays.asList("A", "B", null, "C"));
  
          assertEquals("A", it.peek());
          assertTrue(it.hasNext());
          assertEquals("A", it.next());
          assertEquals("B", it.peek());
          assertTrue(it.hasNext());
          assertEquals("B", it.next());
          assertNull(it.peek());
          assertTrue(it.hasNext());
          assertNull(it.next());
          assertEquals("C", it.peek());
          assertTrue(it.hasNext());
          assertEquals("C", it.next());
          assertEquals("A", it.peek());
          assertTrue(it.hasNext());
          assertEquals("A", it.next());
          assertEquals("B", it.peek());
  
          // Check that peek does not have any side-effects
          assertEquals("B", it.peek());
      }
  
  }
  