PatternTest.java

package com.hanserwei.patterns.iterator;

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 java.util.Iterator;
import java.util.NoSuchElementException;
import org.junit.jupiter.api.Test;

/** 验证本模式的协作契约与边界行为. */
public final class PatternTest {
  /** 创建迭代器后新增内容不会进入旧快照，每个游标独立. */
  @Test
  void isolatesSnapshotAndCursor() {
    ReadingList list = new ReadingList();
    list.add("Java");
    Iterator<String> first = list.iterator();
    list.add("OOP");
    Iterator<String> second = list.iterator();
    assertEquals("Java", first.next());
    assertFalse(first.hasNext());
    assertEquals("Java", second.next());
    assertEquals("OOP", second.next());
  }

  /** 空列表、耗尽和不支持删除均遵守集合协议. */
  @Test
  void obeysIteratorContract() {
    Iterator<String> iterator = new ReadingList().iterator();
    assertFalse(iterator.hasNext());
    assertThrows(NoSuchElementException.class, iterator::next);
    assertThrows(UnsupportedOperationException.class, iterator::remove);
  }
}