content: package com.annimon.stream.streamtests;
  
  import com.annimon.stream.Functions;
  import com.annimon.stream.Stream;
  import java.util.NoSuchElementException;
  import org.junit.Test;
  import static org.hamcrest.MatcherAssert.assertThat;
  import static org.hamcrest.Matchers.is;
  
  public final class SingleTest {
  
      @Test(expected = NoSuchElementException.class)
      public void testSingleOnEmptyStream() {
          Stream.empty().single();
      }
  
      @Test
      public void testSingleOnOneElementStream() {
          Integer result = Stream.of(42).single();
  
          assertThat(result, is(42));
      }
  
      @Test(expected = IllegalStateException.class)
      public void testSingleOnMoreElementsStream() {
          Stream.rangeClosed(1, 2).single();
      }
  
      @Test(expected = NoSuchElementException.class)
      public void testSingleAfterFilteringToEmptyStream() {
          Stream.range(1, 5)
                  .filter(Functions.remainder(6))
                  .single();
      }
  
      @Test
      public void testSingleAfterFilteringToOneElementStream() {
          Integer result = Stream.range(1, 10)
                  .filter(Functions.remainder(6))
                  .single();
  
          assertThat(result, is(6));
      }
  
      @Test(expected = IllegalStateException.class)
      public void testSingleAfterFilteringToMoreElementStream() {
          Stream.range(1, 100)
                  .filter(Functions.remainder(6))
                  .single();
      }
  }
  