Function test_merge_combinations

pandas/tests/reshape/merge/test_merge.py:3014–3084

(
    join_type,
    sort,
    on_index,
    left_unique,
    left_monotonic,
    right_unique,
    right_monotonic,
)

@pytest.mark.parametrize("right_unique", [True, False])
@pytest.mark.parametrize("right_monotonic", [True, False])
def test_merge_combinations(
    join_type,
    sort,
    on_index,
    left_unique,
    left_monotonic,
    right_unique,
    right_monotonic,
):
    how = join_type
    # GH 54611
    left = [2, 3]
    if left_unique:
        left.append(4 if left_monotonic else 1)
    else:
        left.append(3 if left_monotonic else 2)

    right = [2, 3]
    if right_unique:
        right.append(4 if right_monotonic else 1)
    else:
        right.append(3 if right_monotonic else 2)

    left = DataFrame({"key": left})
    right = DataFrame({"key": right})

    if on_index:
        left = left.set_index("key")
        right = right.set_index("key")
        on_kwargs = {"left_index": True, "right_index": True}
    else:
        on_kwargs = {"on": "key"}

    result = merge(left, right, how=how, sort=sort, **on_kwargs)

    if on_index:
        left = left.reset_index()
        right = right.reset_index()

    if how in ["left", "right", "inner"]:
        if how in ["left", "inner"]:
            expected, other, other_unique = left, right, right_unique
        else:
            expected, other, other_unique = right, left, left_unique
        if how == "inner":
            keep_values = set(left["key"].values).intersection(right["key"].values)
            keep_mask = expected["key"].isin(keep_values)
            expected = expected[keep_mask]
        if sort:
            expected = expected.sort_values("key")
        if not other_unique:
            other_value_counts = other["key"].value_counts()
            repeats = other_value_counts.reindex(expected["key"].values, fill_value=1)
            repeats = repeats.astype(np.intp)
            expected = expected["key"].repeat(repeats.values)
            expected = expected.to_frame()
    elif how == "outer":
        left_counts = left["key"].value_counts()