PyTest Snapshot Test Utility
Syrupy is a pytest snapshot plugin. It enables developers to write tests which assert immutability of computed results.
The most popular snapshot test plugin compatible with pytest has some core limitations which this package attempts to address by upholding some key values:
- Extensible: If a particular data type is not supported, users should be able to easily and quickly add support.
- Idiomatic: Snapshot testing should fit naturally among other tests cases in pytest, e.g.
assert x == snapshotvs.
- Soundness: Snapshot tests should uncover even the most minute issues. Unlike other snapshot libraries, Syrupy will fail a test suite if a snapshot does not exist, not just on snapshot differences.
python -m pip install syrupy
Syrupy is a drop in replacement for
snapshottest. If you already have snapshot tests written, it is as easy as:
pip uninstall snapshottest
This is neccessary to prevent argument conflicts.
In a pytest test file
def test_foo(snapshot): actual = "Some computed value!" assert actual == snapshot
when you run
pytest, the above test should fail due to a missing snapshot. Re-run pytest with the update snapshots flag like so:
A snapshot file should be generated under a
__snapshots__ directory in the same directory as
__snapshots__ directory and all its children should be committed along with your test code.
The default serializer supports all python built-in types and provides a sensible default for custom objects.
If you need to customise your object snapshot, is as easy as overriding the default
def __repr__(self) -> str: return "MyCustomClass(...)"
These are the cli options exposed to
pytest by the plugin.
||When supplied updates existing snapshots of any run tests, as well as deleting unused and generating new snapshots.|
||Syrupy default behaviour is to fail the test session when there any unused snapshots. This instructs the plugin not to fail.|
Syrupy comes with a few built-in preset configurations for you to choose from. You should also feel free to extend the
AbstractSyrupyExtension if your project has a need not captured by one our built-ins.
AmberSnapshotExtension: This is the default extension which generates
.ambrfiles. Serialization of most data types are supported, however non-sortable types such as frozenset are experimental.
SingleFileSnapshotExtension: Unlike the
AmberSnapshotExtension, which groups all tests within a single test file into a singular snapshot file, and creates one
.rawfile per test case.
PNGSnapshotExtension: An extension of single file, this should be used to produce
SVGSnapshotExtension: Another extension of single file. This produces
.svgfiles from an svg string.
By overriding the provided
AbstractSnapshotExtension you can implement varied custom behaviours.
See examples of how syrupy can be used and extended in the test examples.
- Custom snapshot directory
- Custom snapshot name
- Custom object snapshots
- JPEG image extension
- Built-in image extensions
pip uninstall syrupy
Feel free to open a PR. This project is still in a very early stage, and we're still figuring out what direction we want to move towards.
To develop locally, clone this repository and run
. script/bootstrap to install test dependencies. You can then use
invoke --list to see available commands.
See contributing guide
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This section is automatically generated via tagging the all-contributors bot in a PR:
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Syrupy is licensed under Apache License Version 2.0.
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