iOS自动化探索自动化测试框架pytest - Assert断言的使用

Posted 2021-02-02 一切都是最好的安排

使用assert语句进行断言

pytest允许使用标准的python assert语法，用来校验expectation and value是否一致

代码演示:

def func():
    return 3

def test_func():
    assert func() == 4
    

执行结果:

(wda_python) bash-3.2$ pytest -q test_assert.py 
F                                                                                                                                  [100%]
================================================================ FAILURES ================================================================
_______________________________________________________________ test_func ________________________________________________________________

    def test_func():
>       assert func() == 4
E       assert 3 == 4
E        +  where 3 = func()

test_assert.py:5: AssertionError
1 failed in 0.07 seconds
(wda_python) bash-3.2$ 

 

同时支持在assert后面添加描述信息:

def func():
    return 3

def test_func():
    assert func() == 4, \'Value was odd, should be even\'

执行结果：

(wda_python) bash-3.2$ pytest -q test_assert.py 
F                                                                                                                                  [100%]
================================================================ FAILURES ================================================================
_______________________________________________________________ test_func ________________________________________________________________

    def test_func():
>       assert func() == 4, \'Value was odd, should be even\'
E       AssertionError: Value was odd, should be even
E       assert 3 == 4
E        +  where 3 = func()

test_assert.py:5: AssertionError
1 failed in 0.07 seconds
(wda_python) bash-3.2$ 

 

预期异常的断言

pytest中使用with pytest.raises: 来断言预期异常

代码演示:

import pytest

def func():
    raise SystemExit(1)

def test_func():
    with pytest.raises(SystemExit):
        func()

执行输出：

(wda_python) bash-3.2$ pytest -q test_sysexit.py 
.                                                                                                                                      [100%]
1 passed in 0.04 seconds
(wda_python) bash-3.2$ 

 

还可以自定义错误描述:

import pytest

def func():
    raise SystemError("Exception 123 raised")

def test_func():
    with pytest.raises(SystemError, match=r\'.* 123 .*\'):
        func()

输出:

(wda_python) bash-3.2$ pytest -q test_assert.py 
.                                                                                                                                  [100%]
1 passed in 0.03 seconds
(wda_python) bash-3.2$ 

如果不匹配的话就会报错:

import pytest

def func():
    raise SystemError("Exception 124 raised")

def test_func():
    with pytest.raises(SystemError, match=r\'.* 123 .*\'):
        func()

输出:

(wda_python) bash-3.2$ pytest -q test_assert.py 
F                                                                                                                                  [100%]
================================================================ FAILURES ================================================================
_______________________________________________________________ test_func ________________________________________________________________

    def test_func():
        with pytest.raises(SystemError, match=r\'.* 123 .*\'):
>           func()
E           AssertionError: Pattern \'.* 123 .*\' not found in \'Exception 124 raised\'

test_assert.py:8: AssertionError
1 failed in 0.07 seconds
(wda_python) bash-3.2$ 

 

断言上下文内容(变量)是否相等

实例代码:

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

运行结果:

(wda_python) bash-3.2$ pytest -q test_assert.py 
F                                                                                                                                  [100%]
================================================================ FAILURES ================================================================
__________________________________________________________ test_set_comparison ___________________________________________________________

    def test_set_comparison():
        set1 = set(\'1308\')
        set2 = set(\'8035\')
>       assert set1 == set2
E       AssertionError: assert set([\'0\', \'1\', \'3\', \'8\']) == set([\'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         - set([\'0\', \'1\', \'3\', \'8\'])
E         ?           -----...
E         
E         ...Full output truncated (3 lines hidden), use \'-vv\' to show

test_assert.py:4: AssertionError
1 failed in 0.10 seconds
(wda_python) bash-3.2$ 

 

自定义断言

官方解释如下

 

我们可以通过实现pytest_assertrepr_compare方法，来自定义assert实现

比如一个Class Foo，我们比较f1和f2

class Foo(object):
    def __init__(self, val):
        self.val = val

    def __eq__(self, other):
        return self.val == other.val

def test_compare():
    f1 = Foo(1)
    f2 = Foo(1)
    assert f1 == f2

运行结果如下:

(wda_python) bash-3.2$ pytest -q test_foocompare.py 
F                                                                                                                                  [100%]
================================================================ FAILURES ================================================================
______________________________________________________________ test_compare ______________________________________________________________

    def test_compare():
        f1 = Foo(1)
        f2 = Foo(2)
>       assert f1 == f2
E       assert <test_foocompare.Foo object at 0x1029eb7d0> == <test_foocompare.Foo object at 0x1029eb290>

test_foocompare.py:11: AssertionError
1 failed in 0.09 seconds
(wda_python) bash-3.2$ 

错误提示不够友好， 我们可以通过完成pytest_assertrepr_compare方法自定义

from test_foocompare import Foo

def pytest_assertrepr_compare(op, left, right):
    if isinstance(left, Foo) and isinstance(right, Foo) and op == "==":
        return [\'Comparing Foo instance:\', \'vals: %s != %s\' % (left.val, right.val)]

运行结果如下:

(wda_python) bash-3.2$ pytest
========================================================== test session starts ===========================================================
platform darwin -- Python 2.7.15, pytest-4.1.0, py-1.7.0, pluggy-0.8.0
rootdir: /Users/jackey/Documents/ios/code/iOS-Auto/Agent_Test, inifile:
collected 1 item                                                                                                                         

test_foocompare.py F                                                                                                               [100%]

================================================================ FAILURES ================================================================
______________________________________________________________ test_compare ______________________________________________________________

    def test_compare():
        f1 = Foo(1)
        f2 = Foo(2)
>       assert f1 == f2
E       assert Comparing Foo instance:
E         vals: 1 != 2

test_foocompare.py:11: AssertionError
======================================================== 1 failed in 0.05 seconds ========================================================
(wda_python) bash-3.2$