@Override
    public boolean isOpen() {
        return internal.isOpen();
    }
@Test
    public void shouldDelegateIsOpen() {
        // `isOpen = true` case
        when(inner.isOpen()).thenReturn(true);
        assertThat(store.isOpen(), is(true));

        // `isOpen = false` case
        when(inner.isOpen()).thenReturn(false);
        assertThat(store.isOpen(), is(false));
    }