使用 pytest 的参数化，如果一个测试用例失败，我如何跳过剩余的测试？

Question

我正在使用pytest.mark.parametrize将越来越长的输入输入到一个相当慢的测试函数中，如下所示：

@pytest.mark.parametrize('data', [
    b'ab',
    b'xyz'*1000,
    b'12345'*1024**2,
    ... # etc
])
def test_compression(data):
    ... # compress the data
    ... # decompress the data
    assert decompressed_data == data

因为压缩大量数据需要很长时间，所以我想在一次失败后跳过所有剩余的测试。 例如，如果测试因输入b'ab' （第一个）而失败，则b'xyz'*1000和b'12345'*1024**2以及所有其他参数化都应跳过（或 xfail 而不执行）。

我知道可以将标记附加到单个参数化，如下所示：

@pytest.mark.parametrize("test_input,expected", [
    ("3+5", 8),
    ("2+4", 6),
    pytest.param("6*9", 42, marks=pytest.mark.xfail),
])

但我不知道如何根据前一个测试用例的状态有条件地应用这些标记。 有没有办法做到这一点？

Answer 1

在执行测试之前评估标记，因此无法传递某种依赖于其他测试结果的声明性标记（如skipif ）。 不过，您可以在挂钩中应用自定义测试跳过逻辑。 修改增量测试 - pytest文档中的测试步骤配方：

# conftest.py
import pytest

def pytest_sessionstart(session):
    session.failednames = set()

def pytest_runtest_makereport(item, call):
    if call.excinfo is not None:
        item.session.failednames.add(item.originalname)

def pytest_runtest_setup(item):
    if item.originalname in item.session.failednames:
        pytest.skip("previous test failed (%s)" % item.name)  # or use pytest.xfail like in the other answer

示例测试

@pytest.mark.parametrize('i', range(10))
def test_spam(i):
    assert i != 3

产量：

=================================== test session starts ===================================
collected 10 items

test_spam.py::test_spam[0] PASSED
test_spam.py::test_spam[1] PASSED
test_spam.py::test_spam[2] PASSED
test_spam.py::test_spam[3] FAILED
test_spam.py::test_spam[4] SKIPPED
test_spam.py::test_spam[5] SKIPPED
test_spam.py::test_spam[6] SKIPPED
test_spam.py::test_spam[7] SKIPPED
test_spam.py::test_spam[8] SKIPPED
test_spam.py::test_spam[9] SKIPPED

========================================= FAILURES ========================================
_______________________________________ test_spam[3] ______________________________________

i = 3

    @pytest.mark.parametrize('i', range(10))
    def test_spam(i):
>       assert i != 3
E       assert 3 != 3

test_spam.py:5: AssertionError
====================== 1 failed, 3 passed, 6 skipped in 0.06 seconds ======================

编辑：使用自定义标记

def pytest_runtest_makereport(item, call):
    markers = {marker.name for marker in item.iter_markers()}
    if call.excinfo is not None and 'skiprest' in markers:
        item.session.failednames.add(item.originalname)

def pytest_runtest_setup(item):
    markers = {marker.name for marker in item.iter_markers()}
    if item.originalname in item.session.failednames and 'skiprest' in markers:
        pytest.skip(item.name)

用法：

@pytest.mark.skiprest
@pytest.mark.parametrize('somearg', ['a', 'b', 'c'])
def test_marked(somearg):
    ...

Answer 2

编辑：我将我的解决方案调整为通过 usint pytest.skip在夹具中接受的解决方案。

以下黑客可以解决您的问题。 假测试函数test_compression总是失败，但只执行一次。 但它要求您在测试函数中添加alrady_failed夹具的检查：

import pytest


@pytest.fixture(scope="function")
def skip_if_already_failed(request, failed=set()):
    key = request.node.name.split("[")[0]
    failed_before = request.session.testsfailed
    if key in failed:
        pytest.skip("previous test {} failed".format(key))
    yield
    failed_after = request.session.testsfailed
    if failed_before != failed_after:
        failed.add(key)


@pytest.mark.parametrize("data", [1, 2, 3, 4, 5, 6])
def test_compression(data, skip_if_already_failed):
    assert data < 3

这是输出：

$ py.test -v sopytest.py
================================== test session starts ==================================
platform darwin -- Python 3.6.6, pytest-3.8.0, py-1.6.0, pluggy-0.7.1 -- ...
cachedir: .pytest_cache
rootdir: ..., inifile:
collected 6 items

sopytest.py::test_compression[1] PASSED                                           [ 16%]
sopytest.py::test_compression[2] PASSED                                           [ 33%]
sopytest.py::test_compression[3] FAILED                                           [ 50%]
sopytest.py::test_compression[4] SKIPPED                                          [ 66%]
sopytest.py::test_compression[5] SKIPPED                                          [ 83%]
sopytest.py::test_compression[6] SKIPPED                                          [100%]

======================================= FAILURES ========================================
__________________________________ test_compression[3] __________________________________

data = 3, skip_if_already_failed = None

    @pytest.mark.parametrize("data", [1, 2, 3, 4, 5, 6])
    def test_compression(data, skip_if_already_failed):
>       assert data < 3
E       assert 3 < 3

sopytest.py:18: AssertionError
===================== 1 failed, 2 passed, 3 skipped in 0.08 seconds =====================

Answer 3

接受的答案不再有效， item.session没有failednames参数。

灵感来自https://docs.pytest.org/en/latest/example/simple.html#incremental-testing-test-steps

还有一种与公认的非常接近的解决方案：

conftest.py

MARKER_SKIPREST = "skiprest"
MARKER_PARAMETRIZE = "parametrize"

_failed_parametrized_tests = set()  # History of failed tests

def pytest_runtest_makereport(item, call):
    """Memorizes names of failed Parametrized tests"""
    marker_names = {marker.name for marker in item.iter_markers()}
    if {MARKER_SKIPREST, MARKER_PARAMETRIZE}.issubset(marker_names):
        if call.excinfo is not None:
            _failed_parametrized_tests.add(item.originalname)


def pytest_runtest_setup(item):
    """Check if the test has already failed with other param.
    If yes - xfail this test"""
    marker_names = {marker.name for marker in item.iter_markers()}
    if {MARKER_SKIPREST, MARKER_PARAMETRIZE}.issubset(marker_names):
        if item.originalname in _failed_parametrized_tests:
            pytest.xfail("Previous test failed")

setup.cfg

[tool:pytest]
markers =
    skiprest: Skip rest of params in parametrized test if one test one of the tests in the sequence has failed.

test_?.py

pytest.mark.skiprest
pytest.mark.parametrize('data', [
    b'ab',
    b'xyz'*1000,
    b'12345'*1024**2,
    ... # etc
])
def test_compression(data):
   ...