return transformValues(table, FIRST_CHARACTER);
  }

  // Null support depends on the underlying table and function.
  @J2ktIncompatible
  @GwtIncompatible // NullPointerTester
  @Override
  public void testNullPointerInstance() {}

  // put() and putAll() aren't supported.
  @Override
  public void testPut() {
    assertThrows(UnsupportedOperationException.class, () -> table.put("foo", 1, 'a'));
    assertSize(0);
  }

    assertThat(table.columnKeySet()).containsExactly(1, 2, 3);
  }

  @J2ktIncompatible
  @GwtIncompatible // NullPointerTester
  public void testNullPointerInstance() {
    table = create("foo", 1, 'a', "bar", 1, 'b', "foo", 2, 'c', "bar", 3, 'd');
    new NullPointerTester().testAllPublicInstanceMethods(table);
  }