pytest-ditto-pyarrow

Extension plugin for pytest-ditto for pyarrow table snapshots.

Use the following marks for their associated recorder:

• @ditto.pyarrow.parquet
• @ditto.pyarrow.feather
• @ditto.pyarrow.csv

Installation

pip install pytest-ditto[pyarrow]

Usage

The following test example tests the result of fn hasn't changed by comparing against a saved snapshot of the result. This snapshot is taken the first time the test is run; hence, the initial run is not a proper test run. Subsequent test runs are compared against the saved result.

• The fixture, table is a pyarrow.Table and is the argument to the function under test, fn.
• fn transforms the data and the test asserts the result of this function in unchanged compared to the initial, hopefully validated, result.
• The output format of the snapshot is parquet as defined by the @ditto.pyarrow.parquet mark.

import pyarrow as pa
import pyarrow.compute as pc
import ditto
import pytest


@pytest.fixture
def table() -> pa.Table:
    return pa.table(
        [
            [1, 2, 3, 4],
            [4.5, 5.2, 6.8, 3.5],
            [7, 8.5, None, None],
            [True, False, True, True],
            ["a", "b", "c", "x"],
        ],
        names=list("abcde"),
    )


def fn(x: pa.Table):
    even_filter = (pc.bit_wise_and(pc.field("a"), pc.scalar(1)) == pc.scalar(0))
    return x.filter(even_filter)


@ditto.pyarrow.parquet
def test_fn_with_pyarrow_parquet_snapshot(snapshot, table):
    result = fn(table)
    assert result.equals(snapshot(result, key="filtered"))