只是添加了另一个“愚蠢”的建议，因为我在现有的答案中没有看到它。本质上，你可以初始化一个错误变量为None，在try/except块中做这件事，然后在那之后检查错误变量的类/值

e = None

try:
    blah()
except Exception as exc:
    e = exc

assert e.__class__ == ValueError # or whatever you expect
assert str(e) == "expected message"

在pytest中有两种方法来处理这类情况:

使用pytest。提出了功能 使用pytest.mark.xfail装饰器

如文档所述:

使用pytest。当您在测试自己的代码故意引发的异常时，而使用@pytest.mark时，则可能会更好。带有检查函数的Xfail可能更适合于记录未修复的错误(其中测试描述了“应该”发生什么)或依赖关系中的错误。

pytest.raise的用法:

def whatever():
    return 9/0
def test_whatever():
    with pytest.raises(ZeroDivisionError):
        whatever()

使用pytest.mark.xfail:

@pytest.mark.xfail(raises=ZeroDivisionError)
def test_whatever():
    whatever()

pytest.raise的输出:

============================= test session starts ============================
platform linux2 -- Python 2.7.10, pytest-3.2.3, py-1.4.34, pluggy-0.4.0 -- 
/usr/local/python_2.7_10/bin/python
cachedir: .cache
rootdir: /home/user, inifile:
collected 1 item

test_fun.py::test_whatever PASSED


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

pytest的输出。xfail标记:

============================= test session starts ============================
platform linux2 -- Python 2.7.10, pytest-3.2.3, py-1.4.34, pluggy-0.4.0 -- 
/usr/local/python_2.7_10/bin/python
cachedir: .cache
rootdir: /home/user, inifile:
collected 1 item

test_fun.py::test_whatever xfail

======================== 1 xfailed in 0.03 seconds=============================

你可以试试

def test_exception():
    with pytest.raises(Exception) as excinfo:   
        function_that_raises_exception()   
    assert str(excinfo.value) == 'some info' 

你的意思是这样的吗?

def test_raises():
    with pytest.raises(Exception) as exc_info:   
        raise Exception('some info')
    # these asserts are identical; you can use either one   
    assert exc_info.value.args[0] == 'some info'
    assert str(exc_info.value) == 'some info'

pytest.raise (Exception)是你所需要的。

Code

import pytest

def test_passes():
    with pytest.raises(Exception) as e_info:
        x = 1 / 0

def test_passes_without_info():
    with pytest.raises(Exception):
        x = 1 / 0

def test_fails():
    with pytest.raises(Exception) as e_info:
        x = 1 / 1

def test_fails_without_info():
    with pytest.raises(Exception):
        x = 1 / 1

# Don't do this. Assertions are caught as exceptions.
def test_passes_but_should_not():
    try:
        x = 1 / 1
        assert False
    except Exception:
        assert True

# Even if the appropriate exception is caught, it is bad style,
# because the test result is less informative
# than it would be with pytest.raises(e)
# (it just says pass or fail.)

def test_passes_but_bad_style():
    try:
        x = 1 / 0
        assert False
    except ZeroDivisionError:
        assert True

def test_fails_but_bad_style():
    try:
        x = 1 / 1
        assert False
    except ZeroDivisionError:
        assert True

输出

============================================================================================= test session starts ==============================================================================================
platform linux2 -- Python 2.7.6 -- py-1.4.26 -- pytest-2.6.4
collected 7 items 

test.py ..FF..F

=================================================================================================== FAILURES ===================================================================================================
__________________________________________________________________________________________________ test_fails __________________________________________________________________________________________________

    def test_fails():
        with pytest.raises(Exception) as e_info:
>           x = 1 / 1
E           Failed: DID NOT RAISE

test.py:13: Failed
___________________________________________________________________________________________ test_fails_without_info ____________________________________________________________________________________________

    def test_fails_without_info():
        with pytest.raises(Exception):
>           x = 1 / 1
E           Failed: DID NOT RAISE

test.py:17: Failed
___________________________________________________________________________________________ test_fails_but_bad_style ___________________________________________________________________________________________

    def test_fails_but_bad_style():
        try:
            x = 1 / 1
>           assert False
E           assert False

test.py:43: AssertionError
====================================================================================== 3 failed, 4 passed in 0.02 seconds ======================================================================================

请注意，e_info保存了异常对象，因此您可以从中提取详细信息。例如，如果您想检查异常调用堆栈或内部的另一个嵌套异常。

如果你想测试特定的错误类型，可以使用try, catch和raise的组合:

#-- test for TypeError
try:
  myList.append_number("a")
  assert False
except TypeError: pass
except: assert False