assertTrue("An Object should be equal to itself.", collection.equals(collection));
  }

  // Comparisons to null *are* defined.
  @SuppressWarnings("UndefinedEquals")
  public void testEquals_null() {
    // noinspection ObjectEqualsNull
    assertFalse("An object should not be equal to null.", collection.equals(null));
  }

  // A collection should essentially never be equal to a non-collection.

    assertTrue("An Object should be equal to itself.", collection.equals(collection));
  }

  // Comparisons to null *are* defined.
  @SuppressWarnings("UndefinedEquals")
  public void testEquals_null() {
    // noinspection ObjectEqualsNull
    assertFalse("An object should not be equal to null.", collection.equals(null));
  }

  // A collection should essentially never be equal to a non-collection.

    assertFalse(entry("foo", 1).equals(control("bar", 1)));
    assertFalse(entry("foo", 1).equals(new Object()));
    assertFalse(entry("foo", 1).equals(null));
  }

  public void testEqualsNull() {
    assertEquals(control(NE, 1), entry(NE, 1));
    assertFalse(control(NE, 1).equals(entry(NE, 2)));
    assertFalse(entry(NE, 1).equals(control("bar", 1)));
    assertFalse(entry(NE, 1).equals(new Object()));

    assertFalse(entry("foo", 1).equals(control("bar", 1)));
    assertFalse(entry("foo", 1).equals(new Object()));
    assertFalse(entry("foo", 1).equals(null));
  }

  public void testEqualsNull() {
    assertEquals(control(NE, 1), entry(NE, 1));
    assertFalse(control(NE, 1).equals(entry(NE, 2)));
    assertFalse(entry(NE, 1).equals(control("bar", 1)));
    assertFalse(entry(NE, 1).equals(new Object()));

    assertFalse(control("foo", 1).equals(entry("foo", 2)));
    assertFalse(foo1.equals(control("bar", 1)));
    assertFalse(foo1.equals(new Object()));
    assertFalse(foo1.equals(null));
  }

  public void testEqualsNull() {
    assertEquals(control(NK, 1), entry(NK, 1));
    assertEquals(control("bar", NV), entry("bar", NV));
    assertFalse(control(NK, 1).equals(entry(NK, 2)));
    assertFalse(entry(NK, 1).equals(control("bar", 1)));