def test_pandas_const_df_prepend():
dta = longley.load_pandas().exog
dta = tools.add_constant(dta, prepend=True)
assert_string_equal('const', dta.columns[0])
assert_equal(dta.var(0)[0], 0)
def test_pandas_const_series_prepend():
dta = longley.load_pandas()
series = dta.exog['GNP']
series = tools.add_constant(series, prepend=True)
assert_string_equal('const', series.columns[0])
assert_equal(series.var(0)[0], 0)
