Testing utilities

[JuroOravec]

I was writing up tests for the icon component package, and I realized that I had to address the same issues with testing components as when I'm writing tests in django-components.

So IMO it'd be helpful if django-components had a way to simplify writing tests.

Some issues with testing components are:

• Component IDs are random, so assertions don't work well
• Components may be already registered
• Our cache of Template instances may have leftover entries

So what I did in the icon package was to wrap that all in a TestEnv class, and then call test_env.setup() and test_env.teardown() in respective methods:

test_env = TestEnv()

class BaseTestCase(SimpleTestCase):
    def setUp(self):
        super().setUp()
        test_env.setup()

    def tearDown(self):
        super().tearDown()
        test_env.teardown()

The implementation looks like this, it's taken from django-components from here:

from typing import List, Optional
from unittest.mock import patch

from django.test import SimpleTestCase

from django_components.component_registry import ComponentRegistry, all_registries

class TestEnv:
    def __init__(self, registries: Optional[List[ComponentRegistry]] = None):
        self.registries = registries or all_registries

    def setup(self):
        self._start_gen_id_patch()

    def teardown(self):
        self._stop_gen_id_patch()

        for registry in self.registries:
            registry.clear()

        from django_components.template import template_cache

        # NOTE: There are 1-2 tests which check Templates, so we need to clear the cache
        if template_cache:
            template_cache.clear()

    # Mock the `generate` function used inside `gen_id` so it returns deterministic IDs
    def _start_gen_id_patch(self):
        # Random number so that the generated IDs are "hex-looking", e.g. a1bc3d
        self._gen_id_count = 10599485

        def mock_gen_id(*args, **kwargs):
            self._gen_id_count += 1
            return hex(self._gen_id_count)[2:]

        self._gen_id_patch = patch("django_components.util.misc.generate", side_effect=mock_gen_id)
        self._gen_id_patch.start()

    def _stop_gen_id_patch(self):
        self._gen_id_patch.stop()
        self._gen_id_count = 10599485

Questions

• Should this be part of the main package, or separate?
• How should it be imported?

I'm thinking that, since it's just one small class right now, it makes sense to include it in the django_components distribution.

So it could be used e.g. like this:

from django_components.testing import TestEnv

test_env = TestEnv()

...

If it ever gets too large, it could be moved into a separate package, and then exposed via django-components as an optional dependency:

pip install django-components[testing]

Notes

As part of this issues we should also document how to test components, and maybe also point to the icon package as a live example.

[EmilStenstrom]

@JuroOravec I think this should be part of the package, available for package builders, and also actually used by the internal tests as well. Could we package our own test logic as a reusable class, use it across tests, and document it as an externally available tool.

[JuroOravec]

100% agree