examples/testing/test_my_functions.py

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"""Unit tests for the plain (un-decorated) Hamilton functions.

The point of these tests: a Hamilton function is just a Python function. You
can import it and call it directly -- no Driver, no DAG, no fixtures required.
"""

import my_functions
import pandas as pd
import pytest


def test_avg_3wk_spend_returns_rolling_mean() -> None:
    spend = pd.Series([10.0, 20.0, 30.0, 40.0])

    result = my_functions.avg_3wk_spend(spend)

    # The first two entries are NaN (window not full), then rolling mean of 3.
    expected = pd.Series([float("nan"), float("nan"), 20.0, 30.0])
    pd.testing.assert_series_equal(result, expected)


def test_spend_per_signup_divides_elementwise() -> None:
    spend = pd.Series([100.0, 200.0])
    signups = pd.Series([10.0, 50.0])

    result = my_functions.spend_per_signup(spend=spend, signups=signups)

    pd.testing.assert_series_equal(result, pd.Series([10.0, 4.0]))


def test_spend_zero_mean_centres_the_series() -> None:
    spend = pd.Series([10.0, 20.0, 30.0])
    spend_mean = 20.0

    result = my_functions.spend_zero_mean(spend=spend, spend_mean=spend_mean)

    pd.testing.assert_series_equal(result, pd.Series([-10.0, 0.0, 10.0]))


@pytest.mark.parametrize(
    ("raw", "expected_first"),
    [
        (pd.Series([0, 1, 2]), 1),  # header sentinel dropped
        (pd.Series([99, 5, 5, 5]), 5),
    ],
)
def test_signups_drops_header_row(raw: pd.Series, expected_first: int) -> None:
    """`pytest.mark.parametrize` is a clean way to cover edge cases."""
    result = my_functions.signups(raw_signups=raw)

    assert result.iloc[0] == expected_first
    assert len(result) == len(raw) - 1