Python的pytest測試框架使用詳解

更新時間：2023年07月26日 09:42:49 作者：Looooking

這篇文章主要介紹了Python的pytest測試框架使用詳解,說到?pytest，大家總不免要拿來和?unittest?來比一下，但是?unittest?畢竟是標準庫，兼容性方面肯定沒得說，但要論簡潔和方便的話，pytest?也是不落下風的,需要的朋友可以參考下

說到 pytest，大家總不免要拿來和 unittest 來比一下，但是 unittest 畢竟是標準庫，兼容性方面肯定沒得說，但要論簡潔和方便的話，pytest 也是不落下風的。

簡單測試示例

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

斷言某類異常

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

將多個測試分組到類

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

在類中對測試分組時需要注意的是，每個測試都有一個唯一的類實例。讓每個測試共享同一個類實例將非常不利于測試隔離（添加到類層級的屬性會被所有 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

指定測試

在模塊中運行測試

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

在模塊中運行特定測試

pytest test.py::TestClassDemoInstance::test_one

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

在目錄中運行測試

pytest testing/

按關鍵字表達式運行測試

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

關于預期異常的斷言

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 ===============================================================================

通過 match 上下文管理器的關鍵字參數(shù)，用于測試正則表達式是否匹配異常的字符串表示形式（如果能正常匹配，則可以通過測試）：

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 斷言給定的異常

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 檢查代碼是否引發(fā)了特定的警告

固定裝置 @pytest.fixture

fixture 是 pytest 的特色，這個我就不多說了。不過，要怎么理解這個 @pytest.fixture 裝飾的函數(shù)呢？

正常來說，像下面的例子，如果函數(shù) test_string 直接把輸入 order 當成一個普通的參數(shù)的話，肯定是會報錯的（畢竟，誰也不知道你這個 order 是什么東東）。但使用了 @pytest.fixture 裝飾 order 以后，就完全不一樣了，這時候，test_string 的輸入?yún)?shù) order 其實是可以看成函數(shù) order 執(zhí)行返回后的結果重新賦值給了 order 參數(shù)（這也很符合裝飾器的特點）。因此，@pytest.fixture 裝飾的測試函數(shù)的參數(shù)相當于是一個已定義函數(shù)執(zhí)行后的結果。

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)

固定裝置有很多特點，比如裝置和使用其他裝置，也可以重復使用，測試函數(shù)和裝置也可以請求一次安裝多個裝置。

固定裝置也可以在同一測試期間多次執(zhí)行，pytest不會為該測試再次執(zhí)行它們（而是使用第一次執(zhí)行后的緩存結果），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 哪個會通過測試呢？答案是：兩個都會通過測試。

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

但是為什么呢？因為對于 test_string1 而言，append_first 使用了固定裝置 order 后， order 已經(jīng)不再是空列表了，即使 test_string1 也有使用 order，但是這個 order 只是第一次 order 被執(zhí)行后的結果的引用，而不會真正去執(zhí)行一遍 order 固定裝置。test_string2 的話就好理解一些了。

到此這篇關于Python的pytest測試框架使用詳解的文章就介紹到這了,更多相關Python的pytest內(nèi)容請搜索腳本之家以前的文章或繼續(xù)瀏覽下面的相關文章希望大家以后多多支持腳本之家！

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