Commentator2.0
573788f75a
Add a snapshot fixture, which allows comparing and updating strings against external files resolves #595 Change-Id: I518f594c601eb7805c6492c0352fca753fda04c9
99 lines
3.9 KiB
Python
99 lines
3.9 KiB
Python
import os
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from collections.abc import Callable
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from logging import Logger
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from pathlib import Path
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from typing import Any
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import pytest
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from _pytest.fixtures import FixtureRequest
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def pytest_addoption(parser: pytest.Parser) -> None:
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"""
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Adds an --accept-tests flag to pytest, which updates .exp files handled by snapshots
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:param parser: pytest parser, which handles the arguments
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"""
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group = parser.getgroup("snapshots")
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group.addoption(
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"--accept-tests",
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action="store_true",
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help="if expected output should be updated",
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dest="accept-tests",
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)
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class Snapshot:
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def __init__(self, expected_output_path: Path, do_update: bool, logger: Logger):
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"""
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A snapshot keeps track of the expected output within the given file.
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If the given file does not exist, an empty string will be assumed as the expected output
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If the `--accept-tests` flag is set or (for legacy reasons) the `_NIX_TEST_ACCEPT` environment variable is set
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The expected output will be updated with the current actual output
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The snapshot must be the **left hand operator** of the equal check.
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Example usage: `snapshot("eval_out.exp") == actual_out`
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:param expected_output_path: where the expected output file is located
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:param do_update: if the output should be updated
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:param logger: logger for debugging stuff, provided by pytest
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"""
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self.expected_output_path = expected_output_path
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# assume empty string, if there is no expected output file (yet)
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self.content = expected_output_path.read_text() if expected_output_path.exists() else ""
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self.do_update = do_update
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self.logger = logger
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def __eq__(self, other: Any) -> bool:
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"""
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Checks if the expected output equals the actual output.
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If the `--accept-tests` flag is set to `1`, the expected output will be updated with the actual output
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:param other: value to compare against, must survive the str() operator
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:return: True if equals or were updated, False if unequal
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"""
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are_equal = self.content == str(other)
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if self.do_update and not are_equal:
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self.expected_output_path.write_text(str(other))
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if not self.expected_output_path.is_symlink():
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self.logger.warning(
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"snapshot didn't propagate, the updated file can be found here: %s",
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self.expected_output_path.absolute(),
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)
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return True
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return are_equal
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def __repr__(self) -> str:
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return f"{self.content!r}"
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def __str__(self) -> str:
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return self.content
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@pytest.fixture
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def snapshot(request: FixtureRequest, logger: Logger, tmp_path: Path) -> Callable[[str], Snapshot]:
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"""
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create a snapshot for the given output file
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the snapshot must be the **left hand operator** of the equal check.
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Example usage: `snapshot("eval_out.exp") == actual_out`
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When either the `--accept-tests` flag or the `_NIX_TEST_ACCEPT` environment variable is set,
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the snapshot will update the expected output with the actual output.
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The given path is relative to the temporary test dir (provided by either `files` or `tmp_path`)
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It is recommended to make the file a symlink back to the file within functional2
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as otherwise the expected output won't be updated.
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:return: a snapshot object which one can use `==` on
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"""
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def create_snapshot(expected_output_path: str) -> Snapshot:
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exp_path = tmp_path / expected_output_path
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if not exp_path.is_symlink():
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logger.warning(
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"expected output file isn't a symlink. When accepting the tests output, the update might not propagate"
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)
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return Snapshot(
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exp_path,
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request.config.getoption("accept-tests")
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or os.environ.get("_NIX_TEST_ACCEPT") is not None,
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logger,
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)
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return create_snapshot
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