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88 lines
3.8 KiB
ReStructuredText
88 lines
3.8 KiB
ReStructuredText
=====
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Tests
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=====
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Telethon uses `Pytest <https://pytest.org/>`__, for testing, `Tox
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<https://tox.readthedocs.io/en/latest/>`__ for environment setup, and
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`pytest-asyncio <https://pypi.org/project/pytest-asyncio/>`__ and `pytest-cov
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<https://pytest-cov.readthedocs.io/en/latest/>`__ for asyncio and
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`coverage <https://coverage.readthedocs.io/>`__ integration.
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While reading the full documentation for these is probably a good idea, there
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is a lot to read, so a brief summary of these tools is provided below for
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convienience.
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Brief Introduction to Pytest
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============================
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`Pytest <https://pytest.org/>`__ is a tool for discovering and running python
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tests, as well as allowing modular reuse of test setup code using fixtures.
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Most Pytest tests will look something like this::
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from module import my_thing, my_other_thing
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def test_my_thing(fixture):
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assert my_thing(fixture) == 42
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@pytest.mark.asyncio
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async def test_my_thing(event_loop):
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assert await my_other_thing(loop=event_loop) == 42
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Note here:
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1. The test imports one specific function. The role of unit tests is to test
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that the implementation of some unit, like a function or class, works.
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It's role is not so much to test that components interact well with each
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other. I/O, such as connecting to remote servers, should be avoided. This
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helps with quickly identifying the source of an error, finding silent
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breakage, and makes it easier to cover all possible code paths.
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System or integration tests can also be useful, but are currently out of
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scope of Telethon's automated testing.
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2. A function ``test_my_thing`` is declared. Pytest searches for files
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starting with ``test_``, classes starting with ``Test`` and executes any
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functions or methods starting with ``test_`` it finds.
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3. The function is declared with a parameter ``fixture``. Fixtures are used to
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request things required to run the test, such as temporary directories,
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free TCP ports, Connections, etc. Fixtures are declared by simply adding
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the fixture name as parameter. A full list of available fixtures can be
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found with the ``pytest --fixtures`` command.
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4. The test uses a simple ``assert`` to test some condition is valid. Pytest
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uses some magic to ensure that the errors from this are readable and easy
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to debug.
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5. The ``pytest.mark.asyncio`` fixture is provided by ``pytest-asyncio``. It
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starts a loop and executes a test function as coroutine. This should be
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used for testing asyncio code. It also declares the ``event_loop``
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fixture, which will request an ``asyncio`` event loop.
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Brief Introduction to Tox
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=========================
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`Tox <https://tox.readthedocs.io/en/latest/>`__ is a tool for automated setup
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of virtual environments for testing. While the tests can be run directly by
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just running ``pytest``, this only tests one specific python version in your
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existing environment, which will not catch e.g. undeclared dependencies, or
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version incompatabilities.
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Tox environments are declared in the ``tox.ini`` file. The default
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environments, declared at the top, can be simply run with ``tox``. The option
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``tox -e py37,flake`` can be used to request specific environments to be run.
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Brief Introduction to Pytest-cov
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================================
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Coverage is a useful metric for testing. It measures the lines of code and
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branches that are exercised by the tests. The higher the coverage, the more
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likely it is that any coding errors will be caught by the tests.
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A brief coverage report can be generated with the ``--cov`` option to ``tox``,
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which will be passed on to ``pytest``. Additionally, the very useful HTML
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report can be generated with ``--cov --cov-report=html``, which contains a
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browsable copy of the source code, annotated with coverage information for each
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line.
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