pytest(4):用例参数化

前言

在真正测试时，我们时常需要用到不同的参数进行传参，如何实现呢？pytest框架 @pytest.mark.parametrize  的方法可以很轻松实现。

@pytest.mark.parametrize

　　应用场景：比如测试登录场景的时候，需要输入不同的测试账号和测试密码，实际上我们不可能写若干个测试用例去测试登录，最好是保持用例不变只变参数，

该方法就是实现这种场景的最佳选择。

1 #测试demo
2 # content of test_expectation.py
3 import pytest
4 #test_input，expected 就是后面对应的参数

5 @pytest.mark.parametrize("test_input,expected", [("3+5", 8), ("2+4", 6), ("6*9", 42)]) 
6 def test_eval(test_input, expected): 
7 　　assert eval(test_input) == expected

运行结果：

 1 $ pytest
 2 =========================== test session starts ============================
 3 platform linux -- Python 3.x.y, pytest-6.x.y, py-1.x.y, pluggy-0.x.y
 4 cachedir: $PYTHON_PREFIX/.pytest_cache
 5 rootdir: $REGENDOC_TMPDIR
 6 collected 3 items
 7 
 8 test_expectation.py ..F                                              [100%]
 9 
10 ================================= FAILURES =================================
11 ____________________________ test_eval[6*9-42] _____________________________
12 
13 test_input = '6*9', expected = 42
14 
15     @pytest.mark.parametrize("test_input,expected", [("3+5", 8), ("2+4", 6), ("6*9", 42)])
16     def test_eval(test_input, expected):
17 >       assert eval(test_input) == expected
18 E       AssertionError: assert 54 == 42
19 E        +  where 54 = eval('6*9')
20 
21 test_expectation.py:6: AssertionError
22 ========================= short test summary info ==========================
23 FAILED test_expectation.py::test_eval[6*9-42] - AssertionError: assert 54...
24 ======================= 1 failed, 2 passed in 0.12s ========================

pytest.mark.xfail

　　表示将该用例标记成xfail失败，并且该用例中的后续代码不会执行。一般这种场景可以用于已经知道此条用例会失败，或者功能未实现

这样可以避免代码重复运行，提高效率。

 1 # content of test_expectation.py
 2 import pytest
 3 
 4 
 5 @pytest.mark.parametrize(
 6     "test_input,expected",
 7     [("3+5", 8), ("2+4", 6), pytest.param("6*9", 42, marks=pytest.mark.xfail)],
 8 )
 9 def test_eval(test_input, expected):
10     assert eval(test_input) == expected

运行结果：

 1 $ pytest
 2 =========================== test session starts ============================
 3 platform linux -- Python 3.x.y, pytest-6.x.y, py-1.x.y, pluggy-0.x.y
 4 cachedir: $PYTHON_PREFIX/.pytest_cache
 5 rootdir: $REGENDOC_TMPDIR
 6 collected 3 items
 7 
 8 test_expectation.py ..x                                              [100%]
 9 
10 ======================= 2 passed, 1 xfailed in 0.12s =======================

两组参数时，就可以组成排列组合的几种结果， x=0/y=2, x=1/y=2, x=0/y=3, and x=1/y=3 四种情况。

1 import pytest
2 
3 
4 @pytest.mark.parametrize("x", [0, 1])
5 @pytest.mark.parametrize("y", [2, 3])
6 def test_foo(x, y):
7     pass

运行结果：

collecting ... collected 4 items

testdemo.py::test_foo[2-0] 
testdemo.py::test_foo[2-1] 
testdemo.py::test_foo[3-0] 
testdemo.py::test_foo[3-1] 

============================== 4 passed in 0.06s ==============================

Process finished with exit code 0
PASSED                                        [ 25%]PASSED

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