}

  public void testCopyOf_shortcut_singleton() {
    Collection<String> c = of("a");
    assertEquals(singleton("a"), copyOf(c));
    assertSame(c, copyOf(c));
  }

  public void testCopyOf_shortcut_sameType() {
    Collection<String> c = of("a", "b", "c");
    assertSame(c, copyOf(c));
  }

  public void testToString() {
    Set<String> set = of("a", "b", "c", "d", "e", "f", "g");