Skip to main content

pytest plugin for writing tests for mypy plugins

Project description

mypy logo

pytest plugin for testing mypy types, stubs, and plugins

Build Status Checked with mypy Gitter


pip install pytest-mypy-plugins



Plugin, after installation, is automatically picked up by pytest therefore it is sufficient to just execute:



The PYTHONPATH and MYPYPATH environment variables, if set, are passed to mypy on invocation. This may be helpful if you are testing a local plugin and need to provide an import path to it.

Be aware that when mypy is run in a subprocess (the default) the test cases are run in temporary working directories where relative paths such as PYTHONPATH=./my_plugin do not reference the directory which you are running pytest from. If you encounter this, consider invoking pytest with --mypy-same-process or make your paths absolute, e.g. PYTHONPATH=$(pwd)/my_plugin pytest.

You can also specify PYTHONPATH, MYPYPATH, or any other environment variable in env: section of yml spec:

- case: mypy_path_from_env
  main: |
    from pair import Pair

    instance: Pair
    reveal_type(instance)  # N: Revealed type is 'pair.Pair'
    - MYPYPATH=./pytest_mypy_plugins/tests/fixtures

What is a test case?

In general each test case is just an element in an array written in a properly formatted YAML file. On top of that, each case must comply to following types:

Property Type Description
case str Name of the test case, complies to [a-zA-Z0-9] pattern
main str Portion of the code as if written in .py file
files Optional[List[File]]=[]* List of extra files to simulate imports if needed
disable_cache Optional[bool]=False Set to true disables mypy caching
mypy_config Optional[Dict[str, Union[str, int, bool, float]]]={} Inline mypy configuration, passed directly to mypy as --config-file option
env Optional[Dict[str, str]]={} Environmental variables to be provided inside of test run
parametrized Optional[List[Parameter]]=[]* List of parameters, similar to @pytest.mark.parametrize
skip str Expression evaluated with following globals set: sys, os, pytest and platform
regex str Allow regular expressions in comments to be matched against actual output. Defaults to "no", i.e. matches full text.

(*) Appendix to pseudo types used above:

class File:
    path: str
    content: Optional[str] = None
Parameter = Mapping[str, Any]

Implementation notes:

  • main must be non-empty string that evaluates to valid Python code,
  • content of each of extra files must evaluate to valid Python code,
  • parametrized entries must all be the objects of the same type. It simply means that each entry must have exact same set of keys,
  • skip - an expression set in skip is passed directly into eval. It is advised to take a peek and learn about how eval works.


1. Inline type expectations

# typesafety/test_request.yml
- case: request_object_has_user_of_type_auth_user_model
  main: |
    from django.http.request import HttpRequest
    reveal_type(HttpRequest().user)  # N: Revealed type is 'myapp.models.MyUser'
    # check that other fields work ok
    reveal_type(HttpRequest().method)  # N: Revealed type is 'Union[builtins.str, None]'
    - path: myapp/
    - path: myapp/
      content: |
        from django.db import models
        class MyUser(models.Model):

2. @parametrized

- case: with_params
    - val: 1
    - val: 1.0
      rt: builtins.float
  main: |
    reveal_type({[ val }})  # N: Revealed type is '{{ rt }}'

3. Longer type expectations

- case: with_out
  main: |
  out: |
    main:1: note: Revealed type is 'builtins.str'

4. Regular expressions in expectations

- case: expected_message_regex_with_out
  regex: yes
  main: |
    a = 'abc'
  out: |
    main:2: note: .*str.*

5. Regular expressions specific lines of output.

- case: expected_single_message_regex
  main: |
    a = 'hello'
    reveal_type(a)  # NR: .*str.*


                        Base directory for tests to use
                        Which .ini file to use as a default config for tests
                        Now, to help with various issues in django-stubs, it runs every single test in the subprocess mypy call.
                        Some debuggers cannot attach to subprocess, so enable this flag to make mypy check happen in the same process.
                        (Could cause cache issues)

Further reading



Project details

Download files

Download the file for your platform. If you're not sure which to choose, learn more about installing packages.

Files for pytest-mypy-plugins, version 1.9.1
Filename, size File type Python version Upload date Hashes
Filename, size pytest_mypy_plugins-1.9.1-py3-none-any.whl (15.8 kB) File type Wheel Python version py3 Upload date Hashes View
Filename, size pytest-mypy-plugins-1.9.1.tar.gz (17.0 kB) File type Source Python version None Upload date Hashes View

Supported by

AWS AWS Cloud computing Datadog Datadog Monitoring DigiCert DigiCert EV certificate Facebook / Instagram Facebook / Instagram PSF Sponsor Fastly Fastly CDN Google Google Object Storage and Download Analytics Microsoft Microsoft PSF Sponsor Pingdom Pingdom Monitoring Salesforce Salesforce PSF Sponsor Sentry Sentry Error logging StatusPage StatusPage Status page