inline-snapshot

create and update inline snapshots in your code.

Features

• records current values during pytest run --update-snapshots=new.
• values are stored in the source code and not in separate files.
• values can be updated with --update-snapshots=failing.

Installation

You can install "inline-snapshot" via pip from PyPI::

$ pip install inline-snapshot

Usage

You can use snapshot() instead of the value which you want to compare with.

def something():
    return 1548 * 18489


def test_something():
    assert something() == snapshot()

You can now run the tests and record the correct values.

$ pytest --update-snapshots=new

def something():
    return 1548 * 18489


def test_something():
    assert something() == snapshot(28620972)  # snapshot gets recorded

Your tests will break if you change your code later. You get normal pytest failure messages, because snapshot(value) just returns value during normal test runs.

def something():
    return (1548 * 18489) // 18  # changed implementation


def test_something():
    assert something() == snapshot(28620972)  # this will fail now

Maybe that is correct and you should fix your code, or your code is correct and you want to update your test results.

$ pytest --update-snapshots=failing

Please verify the new results. git diff will give you a good overview over all changed results. Use pytest -k test_something --update-snapshots=failing if you only want to change one test.

def something():
    return (1548 * 18489) // 18


def test_something():
    assert something() == snapshot(1590054)

The code is generated without any formatting. Use the formatter of your choice to make it look nice, or maybe use darker if you only want to format your changes.

More than just numbers

Requirements:

• snapshot(value) can only be used for == comparison
• the values should be comparable with ==
• repr(value) should return valid python code

You can use almost any python datatype and also complex values like datatime.date (you have to import the right modules to match the repr() output).

from inline_snapshot import snapshot
import datetime


def something():
    return {
        "name": "hello",
        "one number": 5,
        "numbers": list(range(10)),
        "sets": {1, 2, 15},
        "datetime": datetime.date(1, 2, 22),
        "complex stuff": 5j + 3,
        "bytes": b"fglecg\n\x22",
    }


def test_something():
    assert something() == snapshot(
        {
            "name": "hello",
            "one number": 5,
            "numbers": [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
            "sets": {1, 2, 15},
            "datetime": datetime.date(1, 2, 22),
            "complex stuff": (3 + 5j),
            "bytes": b'fglecg\n"',
        }
    )

snapshot() can also be used in loops.

from inline_snapshot import snapshot


def test_loop():
    for name in ["Mia", "Ava", "Leo"]:
        assert len(name) == snapshot(3)

… and more to come :grin:.

Contributing

Contributions are very welcome. Tests can be run with tox. Please use pre-commit for your commits.

License

Distributed under the terms of the MIT license, "inline-snapshot" is free and open source software

Issues

If you encounter any problems, please file an issue along with a detailed description.