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https://github.com/syrusakbary/snapshottest

Snapshot Testing utils for Python 📸
https://github.com/syrusakbary/snapshottest

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Snapshot Testing utils for Python 📸

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# SnapshotTest [![travis][travis-image]][travis-url] [![pypi][pypi-image]][pypi-url]



[travis-image]: https://img.shields.io/travis/syrusakbary/snapshottest.svg?style=flat

[travis-url]: https://travis-ci.org/syrusakbary/snapshottest

[pypi-image]: https://img.shields.io/pypi/v/snapshottest.svg?style=flat

[pypi-url]: https://pypi.python.org/pypi/snapshottest



Snapshot testing is a way to test your APIs without writing actual test cases.



1. A snapshot is a single state of your API, saved in a file.

2. You have a set of snapshots for your API endpoints.

3. Once you add a new feature, you can generate *automatically* new snapshots for the updated API.



## Installation



    $ pip install snapshottest



## Usage with unittest/nose



```python

from snapshottest import TestCase



class APITestCase(TestCase):

    def test_api_me(self):

        """Testing the API for /me"""

        my_api_response = api.client.get('/me')

        self.assertMatchSnapshot(my_api_response)



        # Set custom snapshot name: `gpg_response`

        my_gpg_response = api.client.get('/me?gpg_key')

        self.assertMatchSnapshot(my_gpg_response, 'gpg_response')

```



If you want to update the snapshots automatically you can use the `nosetests --snapshot-update`.



Check the [Unittest example](https://github.com/syrusakbary/snapshottest/tree/master/examples/unittest).



## Usage with pytest



```python

def test_mything(snapshot):

    """Testing the API for /me"""

    my_api_response = api.client.get('/me')

    snapshot.assert_match(my_api_response)



    # Set custom snapshot name: `gpg_response`

    my_gpg_response = api.client.get('/me?gpg_key')

    snapshot.assert_match(my_gpg_response, 'gpg_response')

```



If you want to update the snapshots automatically you can use the `--snapshot-update` config.



Check the [Pytest example](https://github.com/syrusakbary/snapshottest/tree/master/examples/pytest).



## Usage with django

Add to your settings:

```python

TEST_RUNNER = 'snapshottest.django.TestRunner'

```

To create your snapshottest:

```python

from snapshottest.django import TestCase



class APITestCase(TestCase):

    def test_api_me(self):

        """Testing the API for /me"""

        my_api_response = api.client.get('/me')

        self.assertMatchSnapshot(my_api_response)

```

If you want to update the snapshots automatically you can use the `python manage.py test --snapshot-update`.

Check the [Django example](https://github.com/syrusakbary/snapshottest/tree/master/examples/django_project).



## Disabling terminal colors



Set the environment variable `ANSI_COLORS_DISABLED` (to any value), e.g. 



    ANSI_COLORS_DISABLED=1 pytest



# Contributing



After cloning this repo and configuring a virtualenv for snapshottest (optional, but highly recommended), ensure dependencies are installed by running:



```sh

make develop

```



After developing, ensure your code is formatted properly by running:

 

```sh

make format-fix

```



and then run the full test suite with:



```sh

make lint

# and

make test

```



To test locally on all supported Python versions, you can use 

[tox](https://tox.readthedocs.io/):



```sh

pip install tox  # (if you haven't before)

tox

```



# Notes



This package is heavily inspired in [jest snapshot testing](https://facebook.github.io/jest/docs/snapshot-testing.html).



# Reasons to use this package



> Most of this content is taken from the [Jest snapshot blogpost](https://facebook.github.io/jest/blog/2016/07/27/jest-14.html).



We want to make it as frictionless as possible to write good tests that are useful.

We observed that when engineers are provided with ready-to-use tools, they end up writing more tests, which in turn results in stable and healthy code bases.



However engineers frequently spend more time writing a test than the component itself. As a result many people stopped writing tests altogether which eventually led to instabilities.



A typical snapshot test case for a mobile app renders a UI component, takes a screenshot, then compares it to a reference image stored alongside the test. The test will fail if the two images do not match: either the change is unexpected, or the screenshot needs to be updated to the new version of the UI component.



## Snapshot Testing with SnapshotTest



A similar approach can be taken when it comes to testing your APIs.

Instead of rendering the graphical UI, which would require building the entire app, you can use a test renderer to quickly generate a serializable value for your API response.



## License



[MIT License](https://github.com/syrusakbary/snapshottest/blob/master/LICENSE)



[![coveralls][coveralls-image]][coveralls-url]



[coveralls-image]: https://coveralls.io/repos/syrusakbary/snapshottest/badge.svg?branch=master&service=github

[coveralls-url]: https://coveralls.io/github/syrusakbary/snapshottest?branch=master