py.test拆卸，查看测试是否失败，并打印子进程输出

Question

如果测试失败，我希望在py.test解压缩中打印子进程输出，或者将它发送到任何其他人类可读的输出。能不能检查一下测试是否在拆卸中失败了？只有在测试失败时才能获得子进程命令输出的其他方法吗？

我的代码：

"""Test different scaffold operations."""
import subprocess

import pytest
from tempfile import mkdtemp


@pytest.fixture(scope='module')
def app_scaffold(request) -> str:
    """py.test fixture to create app scaffold."""

    folder = mkdtemp(prefix="websauna_test_")

    cmdline = ["..."]

    worker = subprocess.Popen(cmdline, stdout=subprocess.PIPE, stderr=subprocess.PIPE)

    worker.wait(timeout=5.0)

    if worker.returncode is not None:
        raise AssertionError("scaffold command did not properly exit: {}".format(" ".join(cmdline)))

    def teardown():
        worker.terminate()
        # XXX: Hard to capture this only on failure for now
        print(worker.stdout.read().decode("utf-8"))
        print(worker.stderr.read().decode("utf-8"))

    request.addfinalizer(teardown)

Answer 1

您可以用在测试中捕获异常的函数来修饰测试。如果有异常，记录进程输出：

import functools
import subprocess

import pytest


def catch_exception(func):
    @functools.wraps(func)
    def wrapper(*args, **kwargs):
        worker = kwargs['app_scaffold']
        try:
            return func(*args, **kwargs)
        except Exception as e:
            print('stdout:', worker.stdout.read().decode("utf-8"))
            print('stderr:', worker.stderr.read().decode("utf-8"))
            raise
    return wrapper


@pytest.fixture(scope='module')
def app_scaffold(request) -> subprocess.Popen:
    """py.test fixture to create app scaffold."""
    cmdline = ["echo", "something"]

    worker = subprocess.Popen(cmdline, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
    worker.wait(timeout=5.0)

    return worker


@catch_exception
def test_foo(app_scaffold):
    assert False

这段代码忽略了示例中的一些细节，但我认为它应该包含处理案例所需的全部内容。

Answer 2

实际上，您可以捕获在使用capsys和capfd固定装置执行期间创建的stdout/stderr：(https://pytest.org/latest/capture.html)

Answer 3

pytest-instafail插件可能很有用

您可以在运行测试时使用--instafail选项。在继续执行其他测试时，立即显示失败的测试失败

参考：https://pypi.python.org/pypi/pytest-instafail