def METHOD_NAME(
    mocker, initial_bookmarks: t.Optional[t.List[str]], supplier_async: bool
) -> None:
    extra_bookmarks = ["foo:bm1", "bar:bm2", "foo:bm1"]
    mock_cls = mocker.MagicMock if supplier_async else mocker.Mock
    supplier = mock_cls(
        return_value=Bookmarks.from_raw_values(extra_bookmarks)
    )
    bmm = bookmark_manager(initial_bookmarks=initial_bookmarks,
                           bookmarks_supplier=supplier)
    received_bookmarks = bmm.get_bookmarks()
    expected_bookmarks = {*extra_bookmarks, *(initial_bookmarks or [])}
    assert sorted(list(received_bookmarks)) == sorted(list(expected_bookmarks))
    if supplier_async:
        supplier.assert_called_once_with()
    else:
        supplier.assert_called_once_with()