• pytest 7 assert断言


      前言:断言是自动化最终的目的,一个用例没有断言,就失去了自动化测试的意义了。

      断言用到的是 assert关键字。之前的介绍,有的测试方法中其实用到了assert断言。简单的来说,就是预期的结果去和实际结果做对比,符合预期结果就是pass,不符合就fail。

    比如以下的一段代码:

    def add(a,b):
        return a+b
    
    def test_assert():
        assert 6 == add(3,4)

    结果:可以看出,判断的结果是6,和方法返回的结果不一致,所以导致失败。从黄色部分的报错信息可以看出,结果不一致。

    test_assert.py F
    test_assert.py:11 (test_assert)
    7 != 6

    Expected :6
    Actual :7
    <Click to see difference>

    def test_assert():
    > assert 6 == add(3,4)
    E assert 6 == 7
    E + where 7 = add(3, 4)

    test_assert.py:13: AssertionError
    [100%]

    =================================== FAILURES ===================================
    _________________________________ test_assert __________________________________

    def test_assert():
    > assert 6 == add(3,4)
    E assert 6 == 7
    E + where 7 = add(3, 4)

    test_assert.py:13: AssertionError

    异常信息提示:如果想在异常的时候输出一些提示信息,这样报错后就方便查看是什么原因了。

    def add(a,b):
        return a+b
    
    def test_assert():
        assert 6 == add(3,4),"方法返回的值不等于6,而是等于{0}".format(add(3,4))

    结果:可以看出黄色部分,这样会写清楚失败的原因,当有多个判断时,可以容易定位问题。

    test_assert.py F
    test_assert.py:12 (test_assert)
    def test_assert():

    > assert 6 == add(3,4),"方法返回的值不等于6,而是等于{0}".format(add(3,4))
    E AssertionError: 方法返回的值不等于6,而是等于7
    E assert 6 == 7
    E + where 7 = add(3, 4)

    test_assert.py:15: AssertionError
    [100%]

    =================================== FAILURES ===================================
    _________________________________ test_assert __________________________________

    def test_assert():

    > assert 6 == add(3,4),"方法返回的值不等于6,而是等于{0}".format(add(3,4))
    E AssertionError: 方法返回的值不等于6,而是等于7
    E assert 6 == 7
    E + where 7 = add(3, 4)

    test_assert.py:15: AssertionError

     异常断言:为了写关于引发异常的断言,可以使用pytest.raises作为上下文管理器:

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

    结果:可以看出并没有报错,正常情况下,不加异常是会报错的。

    ============================= test session starts ==============================
    platform darwin -- Python 2.7.10, pytest-3.6.3, py-1.5.2, pluggy-0.6.0
    rootdir: /Users/newcomer/PycharmProjects/error/wuya/pytestDemo, inifile:
    plugins: metadata-1.7.0, html-1.19.0, D3-2.0.13, cov-2.5.1, catchlog-1.2.2, allure-adaptor-1.7.10, georaven-17.1.0.170collected 1 item

    test_assert.py . [100%]

    -- Docs: http://doc.pytest.org/en/latest/warnings.html
    ===================== 1 passed, 1 warnings in 0.01 seconds =====================

    以上,我们要断言它抛的异常是不是预期的,比如执行:1/0,预期结果是抛异常:ZeroDivisionError: division by zero,那我们要断言这个异常。通常是断言异常的type和value的值。这里1/0的异常类型是ZeroDivisionError,异常的value值是"integer division or modulo by zero",于是以下是代码的设计用例:

    import pytest
    
    def test_zero_division():
        with pytest.raises(ZeroDivisionError,message="Exceptions ZeroDivisionError") as exinfo:
            1/0
    
        assert exinfo.type == ZeroDivisionError
        assert str(exinfo.value) == "integer division or modulo by zero","{0}".format(exinfo.value)

    结果:可以看出来,通过了一个测试用例,但是需要注意,需要把value的值转换成str类型的才可以比较,而且值是要加引号的。断言type的时候,不需要给异常类型添加引号。
    raises里面的message关键字参数消息指定自定义失败消息

    ============================= test session starts ==============================
    platform darwin -- Python 2.7.10, pytest-3.6.3, py-1.5.2, pluggy-0.6.0
    rootdir: /Users/newcomer/PycharmProjects/error/wuya/pytestDemo, inifile:
    plugins: metadata-1.7.0, html-1.19.0, D3-2.0.13, cov-2.5.1, catchlog-1.2.2, allure-adaptor-1.7.10, georaven-17.1.0.170collected 1 item

    test_assert.py .exinfo.type: <type 'exceptions.ZeroDivisionError'>
    exinfo.value: integer division or modulo by zero
    [100%]

    ===================== 1 passed, 1 warnings in 0.01 seconds =====================

    import pytest
    
    def test_exception():
        with pytest.raises(ZeroDivisionError,message="Exception ZeroDivisionError") as exinfo:
           pass

    结果:可以看出来,结果中的异常是message自己定义的信息

    =================================== FAILURES ===================================
    ________________________________ test_exception ________________________________

    
    

    def test_exception():
    with pytest.raises(ZeroDivisionError,message="Exception ZeroDivisionError") as exinfo:
    > pass
    E Failed: Exception ZeroDivisionError

    
    

    test_assert.py:28: Failed

    ================ 1 failed, 1 warnings in 0.08 seconds ================

     

    常用断言:pytest里面的断言实际上就是python里面assert的断言方法,常用以下几种:

    ·assert xx  判断xx为真

    ·assert not xx 判断xx不为真

    ·assert a in b 判断b包含a

    ·assert a == b 判断a等于b

    ·assert a != b 判断a不等于b

    def is_true(num):
        if num>0:
            return True
        else:
            return False
    
    def test_01():
        """判断是不是为真"""
        a = 5
        b = -1
        assert is_true(a)
        assert not is_true(b)
    
    def test_02():
        """判断b包含a"""
        a = "hello"
        b = "hello world"
        assert a in b
    
    def test_03():
        """判断是否相等"""
        a = "hello"
        b = "hello"
        c = "hello world"
        assert a == b
        assert a != c

    结果:由此可以看出来,三个用例都执行成功。

    ============================= test session starts ==============================
    platform darwin -- Python 2.7.10, pytest-3.6.3, py-1.5.2, pluggy-0.6.0
    rootdir: /Users/newcomer/PycharmProjects/error/wuya/pytestDemo, inifile:
    plugins: metadata-1.7.0, html-1.19.0, D3-2.0.13, cov-2.5.1, catchlog-1.2.2, allure-adaptor-1.7.10, georaven-17.1.0.170collected 3 items

    test_assert.py ... [100%]

    =============================== warnings summary ===============================
    <undetermined location>
    pytest-catchlog plugin has been merged into the core, please remove it from your requirements.

    -- Docs: http://doc.pytest.org/en/latest/warnings.html
    ===================== 3 passed, 1 warnings in 0.02 seconds =====================

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  • 原文地址:https://www.cnblogs.com/peiminer/p/9494536.html
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