Python的pytest测试框架使用详解

更新时间：2023年07月26日 09:42:49 作者：Looooking

这篇文章主要介绍了Python的pytest测试框架使用详解,说到 pytest，大家总不免要拿来和 unittest 来比一下，但是 unittest 毕竟是标准库，兼容性方面肯定没得说，但要论简洁和方便的话，pytest 也是不落下风的,需要的朋友可以参考下

说到 pytest，大家总不免要拿来和 unittest 来比一下，但是 unittest 毕竟是标准库，兼容性方面肯定没得说，但要论简洁和方便的话，pytest 也是不落下风的。

简单测试示例

def func(x):
    return x + 1
def test_answer():
    assert func(3) == 5

Testing started at 15:57 ...
Launching pytest with arguments test.py::test_answer --no-header --no-summary -q in D:\Projects\insight-tools-rest

============================= test session starts =============================
collecting ... collected 1 item

test.py::test_answer FAILED [100%]
test.py:4 (test_answer)
4 != 5

Expected :5
Actual :4
<Click to see difference>

def test_answer():
> assert func(3) == 5
E assert 4 == 5

test.py:6: AssertionError

============================== 1 failed in 0.13s ==============================

Process finished with exit code 1

断言某类异常

import pytest
def f():
    raise SystemExit(1)
def test_mytest():
    with pytest.raises(SystemExit):
        f()

[root@master ~]# pytest test.py
============================================================================= test session starts ==============================================================================
platform linux -- Python 3.6.8, pytest-6.2.5, py-1.11.0, pluggy-1.0.0
rootdir: /root
collected 1 item

test.py . [100%]

============================================================================== 1 passed in 0.01s ===============================================================================

[root@master ~]# pytest -q test.py
. [100%]
1 passed in 0.00s

将多个测试分组到类

class TestClass:
    def test_one(self):
        x = "this"
        assert "h" in x
    def test_two(self):
        x = "hello"
        assert hasattr(x, "check")

[root@master ~]# pytest -q test.py
.F [100%]
=================================================================================== FAILURES ===================================================================================
______________________________________________________________________________ TestClass.test_two ______________________________________________________________________________

self = <test.TestClass object at 0x7ff2dec24390>

def test_two(self):
x = "hello"
> assert hasattr(x, "check")
E AssertionError: assert False
E + where False = hasattr('hello', 'check')

test.py:8: AssertionError
=========================================================================== short test summary info ============================================================================
FAILED test.py::TestClass::test_two - AssertionError: assert False
1 failed, 1 passed in 0.02s

在类中对测试分组时需要注意的是，每个测试都有一个唯一的类实例。让每个测试共享同一个类实例将非常不利于测试隔离（添加到类层级的属性会被所有 test 共享）。

 
class TestClassDemoInstance:
    value = 0
    def test_one(self):
        self.value = 1
        assert self.value == 1
    def test_two(self):
        assert self.value == 1

[root@master ~]# pytest -q test.py
.F [100%]
=================================================================================== FAILURES ===================================================================================
________________________________________________________________________ TestClassDemoInstance.test_two ________________________________________________________________________

self = <test.TestClassDemoInstance object at 0x7f22110f44e0>

def test_two(self):
> assert self.value == 1
E assert 0 == 1
E + where 0 = <test.TestClassDemoInstance object at 0x7f22110f44e0>.value

test.py:9: AssertionError
=========================================================================== short test summary info ============================================================================
FAILED test.py::TestClassDemoInstance::test_two - assert 0 == 1
1 failed, 1 passed in 0.02s

指定测试

在模块中运行测试

pytest test.py

[root@master ~]# pytest -q test.py
.F [100%]
=================================================================================== FAILURES ===================================================================================
________________________________________________________________________ TestClassDemoInstance.test_two ________________________________________________________________________

self = <test.TestClassDemoInstance object at 0x7f3395b78470>

def test_two(self):
> assert self.value == 1
E assert 0 == 1
E + where 0 = <test.TestClassDemoInstance object at 0x7f3395b78470>.value

test.py:9: AssertionError
=========================================================================== short test summary info ============================================================================
FAILED test.py::TestClassDemoInstance::test_two - assert 0 == 1
1 failed, 1 passed in 0.02s

在模块中运行特定测试

pytest test.py::TestClassDemoInstance::test_one

[root@master ~]# pytest -q test.py::TestClassDemoInstance::test_one
. [100%]
1 passed in 0.01s

在目录中运行测试

pytest testing/

按关键字表达式运行测试

pytest -k "MyClass and not method"

[root@master ~]# pytest -q test.py -k 'one'
. [100%]
1 passed, 1 deselected in 0.01s

[root@master ~]# pytest -q test.py -k 'two'
F [100%]
=================================================================================== FAILURES ===================================================================================
________________________________________________________________________ TestClassDemoInstance.test_two ________________________________________________________________________

self = <test.TestClassDemoInstance object at 0x7fbbe853e908>

def test_two(self):
> assert self.value == 1
E assert 0 == 1
E + where 0 = <test.TestClassDemoInstance object at 0x7fbbe853e908>.value

test.py:9: AssertionError
=========================================================================== short test summary info ============================================================================
FAILED test.py::TestClassDemoInstance::test_two - assert 0 == 1
1 failed, 1 deselected in 0.02s

关于预期异常的断言

import pytest
def test_zero_division():
    with pytest.raises(ZeroDivisionError):
        1 / 0

root@master ~# pytest test.py
============================================================================= test session starts ==============================================================================
platform linux -- Python 3.6.8, pytest-6.2.5, py-1.11.0, pluggy-1.0.0
rootdir: /root
collected 1 item

test.py . [100%]

============================================================================== 1 passed in 0.02s ===============================================================================

通过 match 上下文管理器的关键字参数，用于测试正则表达式是否匹配异常的字符串表示形式（如果能正常匹配，则可以通过测试）：

import pytest
def myfunc():
    raise ValueError("Exception 123 raised")
def test_match():
    #with pytest.raises(ValueError, match=r".* 123 .*"):
    with pytest.raises(ValueError, match=r".* 124 .*"):
        myfunc()

root@master ~# pytest -q test.py
F [100%]
=================================================================================== FAILURES ===================================================================================
__________________________________________________________________________________ test_match __________________________________________________________________________________

def test_match():
#with pytest.raises(ValueError, match=r".* 123 .*"):
with pytest.raises(ValueError, match=r".* 124 .*"):
> myfunc()

test.py:11:
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

def myfunc():
> raise ValueError("Exception 123 raised")
E ValueError: Exception 123 raised

test.py:5: ValueError

During handling of the above exception, another exception occurred:

def test_match():
#with pytest.raises(ValueError, match=r".* 123 .*"):
with pytest.raises(ValueError, match=r".* 124 .*"):
> myfunc()
E AssertionError: Regex pattern '.* 124 .*' does not match 'Exception 123 raised'.

test.py:11: AssertionError
=========================================================================== short test summary info ============================================================================
FAILED test.py::test_match - AssertionError: Regex pattern '.* 124 .*' does not match 'Exception 123 raised'.
1 failed in 0.02s

def test_set_comparison():
    set1 = set("1308")
    set2 = set("8035")
    assert set1 == set2

root@master ~# pytest -q test.py
F [100%]
=================================================================================== FAILURES ===================================================================================
_____________________________________________________________________________ test_set_comparison ______________________________________________________________________________

def test_set_comparison():
set1 = set("1308")
set2 = set("8035")
> assert set1 == set2
E AssertionError: assert {'0', '1', '3', '8'} == {'0', '3', '5', '8'}
E Extra items in the left set:
E '1'
E Extra items in the right set:
E '5'
E Full diff:
E - {'3', '8', '0', '5'}
E + {'8', '3', '1', '0'}

test.py:4: AssertionError
=========================================================================== short test summary info ============================================================================
FAILED test.py::test_set_comparison - AssertionError: assert {'0', '1', '3', '8'} == {'0', '3', '5', '8'}
1 failed in 0.02s

使用 pytest.raises 断言给定的异常

import pytest
@pytest.mark.xfail(raises=IndexError)
def test_f():
    a = [1, 2]
    print(a[0])

root@master ~# pytest -q test.py
X [100%]
1 xpassed in 0.01s

import pytest
@pytest.mark.xfail(raises=IndexError)
def test_f():
    a = [1, 2]
    print(a[2])

root@master ~# pytest -q test.py
x [100%]
1 xfailed in 0.02s

也可以使用 pytest.warns 检查代码是否引发了特定的警告

固定装置 @pytest.fixture

fixture 是 pytest 的特色，这个我就不多说了。不过，要怎么理解这个 @pytest.fixture 装饰的函数呢？

正常来说，像下面的例子，如果函数 test_string 直接把输入 order 当成一个普通的参数的话，肯定是会报错的（毕竟，谁也不知道你这个 order 是什么东东）。但使用了 @pytest.fixture 装饰 order 以后，就完全不一样了，这时候，test_string 的输入参数 order 其实是可以看成函数 order 执行返回后的结果重新赋值给了 order 参数（这也很符合装饰器的特点）。因此，@pytest.fixture 装饰的测试函数的参数相当于是一个已定义函数执行后的结果。

import pytest
# Arrange
@pytest.fixture
def first_entry():
    return "a"
# Arrange
@pytest.fixture
def order(first_entry):
    return [first_entry]
def test_string(order):
    # Act
    order.append("b")
    # Assert
    assert order == ["a", "b"]

 
def first_entry():
    return "a"
def order(first_entry):
    return [first_entry]
def test_string(order):
    # Act
    order.append("b")
    # Assert
    assert order == ["a", "b"]
entry = first_entry()
the_list = order(first_entry=entry)
test_string(order=the_list)

固定装置有很多特点，比如装置和使用其他装置，也可以重复使用，测试函数和装置也可以请求一次安装多个装置。

固定装置也可以在同一测试期间多次执行，pytest不会为该测试再次执行它们（而是使用第一次执行后的缓存结果），比如下面的例子：

import pytest
# Arrange
@pytest.fixture
def first_entry():
    return "a"
# Arrange
@pytest.fixture
def order():
    return []
# Act
@pytest.fixture
def append_first(order, first_entry):
    return order.append(first_entry)
def test_string1(append_first, order, first_entry):
    # Assert
    assert order == [first_entry]
def test_string2(order, first_entry):
    # Assert
    assert order == []

test_string1 和 test_string2 哪个会通过测试呢？答案是：两个都会通过测试。

root@master ~# pytest -q test.py
.. [100%]
2 passed in 0.01s

但是为什么呢？因为对于 test_string1 而言，append_first 使用了固定装置 order 后， order 已经不再是空列表了，即使 test_string1 也有使用 order，但是这个 order 只是第一次 order 被执行后的结果的引用，而不会真正去执行一遍 order 固定装置。test_string2 的话就好理解一些了。

到此这篇关于Python的pytest测试框架使用详解的文章就介绍到这了,更多相关Python的pytest内容请搜索脚本之家以前的文章或继续浏览下面的相关文章希望大家以后多多支持脚本之家！

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