def test_nan_stays_float():
# GH 7031
idx0 = MultiIndex(levels=[["A", "B"], []],
codes=[[1, 0], [-1, -1]],
names=[0, 1])
idx1 = MultiIndex(levels=[["C"], ["D"]], codes=[[0], [0]], names=[0, 1])
idxm = idx0.join(idx1, how="outer")
assert pd.isna(idx0.get_level_values(1)).all()
# the following failed in 0.14.1
assert pd.isna(idxm.get_level_values(1)[:-1]).all()
df0 = pd.DataFrame([[1, 2]], index=idx0)
df1 = pd.DataFrame([[3, 4]], index=idx1)
dfm = df0 - df1
assert pd.isna(df0.index.get_level_values(1)).all()
# the following failed in 0.14.1
assert pd.isna(dfm.index.get_level_values(1)[:-1]).all()
