def METHOD_NAME(df_factory):
    # Create test databn
    x = np.array([None, 'A', 'B', -1, 0, 2, '', '', None, None, None, np.nan, np.nan, np.nan, np.nan])
    df = df_factory(x=x)
    uniques = df.x.unique(dropnan=True)
    assert set(uniques) == set(['', 'A', 'B', -1, 0, 2, None])