编写一个 pytest 函数来检查控制台上的输出 (stdout) [英] Writing a pytest function for checking the output on console (stdout)

问题描述

此链接 描述了如何使用 pytest 捕获控制台输出.我尝试了以下简单代码，但出现错误

This link gives a description how to use pytest for capturing console outputs. I tried on this following simple code, but I get error

import sys
import pytest
def f(name):
    print "hello "+ name

def test_add(capsys):
    f("Tom")
    out,err=capsys.readouterr()
    assert out=="hello Tom"


test_add(sys.stdout)

输出:

python test_pytest.py 
hello Tom
Traceback (most recent call last):
  File "test_pytest.py", line 12, in <module>
    test_add(sys.stdout)
  File "test_pytest.py", line 8, in test_add
    out,err=capsys.readouterr()
AttributeError: 'file' object has no attribute 'readouterr'

出了什么问题，需要什么修复?谢谢

what is wrong and what fix needed? thank you

根据评论，我更改了 capfd，但仍然出现相同的错误

As per the comment, I changed capfd, but I still get the same error

import sys
import pytest
def f(name):
    print "hello "+ name

def test_add(capfd):
    f("Tom")
    out,err=capfd.readouterr()
    assert out=="hello Tom"


test_add(sys.stdout)

推荐答案

使用 capfd 固定装置.

示例:

def test_foo(capfd):
    foo()  # Writes "Hello World!" to stdout
    out, err = capfd.readouterr()
    assert out == "Hello World!"

参见:http://pytest.org/en/latest/fixture.html 了解更多详情

请参阅:py.test --fixtures 以获取内置设备列表.

And see: py.test --fixtures for a list of builtin fixtures.

您的示例存在一些问题.这是一个更正的版本:

Your example has a few problems. Here is a corrected version:

def f(name):
    print "hello {}".format(name)


def test_f(capfd):
    f("Tom")

    out, err = capfd.readouterr()
    assert out == "hello Tom\n"

注意:

• 不要使用 sys.stdout -- 使用 pytest 提供的 capfd 固定装置.
• 运行测试:py.test foo.py

• Do not use sys.stdout -- Use the capfd fixture as-is as provided by pytest.
• Run the test with: py.test foo.py

测试运行输出:

$ py.test foo.py
====================================================================== test session starts ======================================================================
platform linux2 -- Python 2.7.5 -- pytest-2.4.2
plugins: flakes, cache, pep8, cov
collected 1 items 

foo.py .

=================================================================== 1 passed in 0.01 seconds ====================================================================

另请注意:

• 您不需要在您的测试模块中运行您的测试功能.py.test(CLI 工具和测试运行程序)为您完成这项工作.

• You do not need to run your Test Function(s) in your test modules. py.test (The CLI tool and Test Runner) does this for you.

py.test 主要做三件事:

py.test does mainly three things:

1. 收集您的测试
2. 运行测试
3. 显示统计信息和可能的错误

默认py.test 寻找(可配置的iirc)test_foo.py 测试模块和test_foo() 在您的测试模块中测试功能.

By default py.test looks for (configurable iirc) test_foo.py test modules and test_foo() test functions in your test modules.

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