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x == snapshot()

General

A snapshot can be compared with any value using ==. The value can be recorded with --inline-snapshot=create if the snapshot is empty. The value can later be changed with --inline-snapshot=fix if the value the snapshot is compared with has changed.

Example:

def test_something():
    assert 2 + 4 == snapshot()


def test_something():
    assert 2 + 4 == snapshot(6)


def test_something():
    assert 2 + 40 == snapshot(4)


def test_something():
    assert 2 + 40 == snapshot(42)

dirty-equals

It might be, that larger snapshots with many lists and dictionaries contain some values which change frequently and are not relevant for the test. They might be part of larger data structures and be difficult to normalize.

Example:

from inline_snapshot import snapshot
import datetime


def get_data():
    return {
        "date": datetime.datetime.utcnow(),
        "payload": "some data",
    }


def test_function():
    assert get_data() == snapshot()


from inline_snapshot import snapshot
import datetime


def get_data():
    return {
        "date": datetime.datetime.utcnow(),
        "payload": "some data",
    }


def test_function():
    assert get_data() == snapshot(
        {"date": datetime.datetime(2024, 3, 14, 0, 0), "payload": "some data"}
    )

inline-snapshot tries to change only the values that it needs to change in order to pass the equality comparison. This allows to replace parts of the snapshot with dirty-equals expressions. This expressions are preserved as long as the == comparison with them is True.

Example:

from inline_snapshot import snapshot
from dirty_equals import IsDatetime
import datetime


def get_data():
    return {
        "date": datetime.datetime.utcnow(),
        "payload": "some data",
    }


def test_function():
    assert get_data() == snapshot(
        {
            "date": IsDatetime(),
            "payload": "some data",
        }
    )


from inline_snapshot import snapshot
from dirty_equals import IsDatetime
import datetime


def get_data():
    return {
        "date": datetime.datetime.utcnow(),
        "payload": "data changed for some good reason",
    }


def test_function():
    assert get_data() == snapshot(
        {
            "date": IsDatetime(),
            "payload": "some data",
        }
    )


from inline_snapshot import snapshot
from dirty_equals import IsDatetime
import datetime


def get_data():
    return {
        "date": datetime.datetime.utcnow(),
        "payload": "data changed for some good reason",
    }


def test_function():
    assert get_data() == snapshot(
        {
            "date": IsDatetime(),
            "payload": "data changed for some good reason",
        }
    )

Note

The current implementation looks only into lists, dictionaries and tuples and not into the representation of other data structures.

pytest options

It interacts with the following --inline-snapshot flags:

  • create create a new value if the snapshot value is undefined.
  • fix record the value parts and store them in the source code if it is different from the current one.
  • update update parts of the value if their representation has changed. Parts which are replaced with dirty-equals expressions are not updated.