inline-snapshot

Installation

You can install “inline-snapshot” via pip:

pip install inline-snapshot

Key Features

• support for normal assertions: inline-snapshot can now also fix normal assertions which do not use snapshot() like:

  assert 1 + 1 == 3
  

  You can learn here more about this feature.

• Intuitive Semantics: snapshot(x) mirrors x for easy understanding.

• Versatile Comparison Support: Equipped with x == snapshot(...), x <= snapshot(...), x in snapshot(...), and snapshot(...)[key].

• No CLI arguments required: you will get a nice report where you can review the snapshot changes when you run pytest (only for CPython > 3.11, you have to use --inline-snapshot=review on older versions).

• Enhanced Control Flags: Utilize various flags for precise control of which snapshots you want to change.

• Preserved Formatting: Retains formatting consistency with Black formatting or a custom format-command.

• External File Storage: Store snapshots externally using external("uuid:eb1167b3-67a9-4378-bc65-c1e582e2e662.json") with support for custom file formats.

• Seamless Pytest Integration: Integrated seamlessly with pytest for effortless testing.

• Integration into normal functions: use snapshot_arg() to convert the arguments of your function into snapshots.

• Customizable: code generation can be customized with @customize

• Nested Snapshot Support: snapshots can contain other snapshots

• Fuzzy Matching: Incorporate dirty-equals for flexible comparisons within snapshots.

• Dynamic Snapshot Content: snapshots can contain non-constant values

• Comprehensive Documentation: Access detailed documentation for complete guidance.

Usage

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

from inline_snapshot import snapshot


def test_something():
    assert 1548 * 18489 == snapshot()

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

$ pytest --inline-snapshot=review

from inline_snapshot import snapshot


def test_something():
    assert 1548 * 18489 == snapshot(28620972)

The following examples show how you can use inline-snapshot in your tests. Take a look at the documentation if you want to know more.

from inline_snapshot import external, outsource, snapshot


def test_something():
    for number in range(5):
        # testing for numeric limits
        assert number <= snapshot()
        assert number >= snapshot()

    for c in "hello world":
        # test if something is part of a set
        assert c in snapshot()

    s = snapshot()

    for number in range(5):
        # create sub-snapshots at runtime
        assert s[number]["square"] == number**2
        assert s[number]["pow_of_two"] == (
            (number & (number - 1) == 0) and number != 0
        )

    assert outsource("large string\n" * 5) == snapshot()

    assert "generates\nmultiline\nstrings" == snapshot()

snapshot_arg() can also be used for function parameters:

import subprocess as sp
import sys
from inline_snapshot import snapshot_arg


def run_python(cmd, stdout="", stderr=""):
    result = sp.run([sys.executable, "-c", cmd], capture_output=True)
    assert result.stdout.decode() == snapshot_arg(stdout)
    assert result.stderr.decode() == snapshot_arg(stderr)


def test_cmd():
    run_python("print('hello world')")

    run_python("1/0")

Feedback

inline-snapshot provides some advanced ways to work with snapshots.

I would like to know how these features are used to further improve this small library. Let me know if you’ve found interesting use cases for this library via 𝕏, fosstodon or in the github discussions.

Sponsors

I would like to thank my sponsors. Without them, I would not be able to invest so much time in my projects.

Gold sponsor 🥇

Bronze sponsor 🥉

I have also started to offer insider features for inline-snapshot. I will only release features as insider features if they will not cause problems for you when used in an open source project. I hope sponsoring will allow me to spend more time working on open source projects. Thank you for using inline-snapshot, the future will be 🚀.

Issues

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

License

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