pytest(16):assume插件:多重断言执行
背景
使用pytest进行断言判断的时候，为了用例的精准性，经常会多个方面进行断言，比如如下：
断言1：断言响应的http的状态
断言2：断言响应返回的code值
断言3：断言响应返回的json中的data字段是否符合预期。
如果使用原生python的assert，就会遇到一个断言失败则全部失败的情况。比如说，断言1结果为Failed，那么断言2和断言3都不会被执行。
我们希望断言2和断言3继续执行，这样我们能获取更多的断言结果来判断出接口哪里出了问题，能够更好地进行问题定位，这时候该本文主角出现了：pytest-assume插件。
简介
一个可以允许pytest测试用例中执行多个失败的断言的插件（即上面断言1，断言2，断言3都失败的情况下，三个断言都能被执行）。
项目：https://github.com/astraw38/pytest-assume
说明：
该插件源自pytest-expect，并且做了一部分小的修改：
1. 支持showlocals(即pytest命令行的'-l'参数, 显示执行过程中的局部变量）。
2. 可以全局使用，无需指定fixtrue装饰器。（即任意test_xxx函数中都能用）。
3. 对断言输出做了一些格式上的美化。
安装
#根据你python版本，可选择pip3或者pip sudo pip3(pip) install git+https://github.com/astraw38/pytest-assume.git #或者 sudo pip3(pip) install pytest-assume
例子
1. 一个对比原生assert和pytest-assume的测试用例
#!/usr/bin/env python3
#!coding:utf-8
import pytest
@pytest.mark.parametrize(('x', 'y'), [(1, 1), (1, 0), (0, 1)])
def test_simple_assume(x, y):
assert x == y #如果这个断言失败，则后续都不会执行
assert True
assert False
@pytest.mark.parametrize(('x', 'y'), [(1, 1), (1, 0), (0, 1)])
def test_pytest_assume(x, y):
pytest.assume(x == y) #即使这个断言失败，后续仍旧执行
pytest.assume(True)
pytest.assume(False)
输入：
===================================================================================== test session starts =====================================================================================
platform darwin -- Python 3.8.2, pytest-6.2.1, py-1.10.0, pluggy-0.13.1
rootdir: /Users/xxx/Desktop/pytest
plugins: assume-2.4.2, ordering-0.6
collected 6 items (这里执行了六个用例）
test_demo.py FFF [100%]
========================================================================================== FAILURES ===========================================================================================
___________________________________________________________________________________ test_simple_assume[1-1] ___________________________________________________________________________________
x = 1, y = 1
@pytest.mark.parametrize(('x', 'y'), [(1, 1), (1, 0), (0, 1)])
def test_simple_assume(x, y):
assert x == y
assert True
> assert False （前两个断言成功，第三个断言失败了）
E assert False
test_demo.py:9: AssertionError
___________________________________________________________________________________ test_simple_assume[1-0] ___________________________________________________________________________________
x = 1, y = 0
@pytest.mark.parametrize(('x', 'y'), [(1, 1), (1, 0), (0, 1)])
def test_simple_assume(x, y):
> assert x == y (第一个断言失败了，后续断言不会被执行）
E assert 1 == 0
test_demo.py:7: AssertionError
___________________________________________________________________________________ test_simple_assume[0-1] ___________________________________________________________________________________
x = 0, y = 1
@pytest.mark.parametrize(('x', 'y'), [(1, 1), (1, 0), (0, 1)])
def test_simple_assume(x, y):
> assert x == y (第一个断言失败了，后续断言不会被执行）
E assert 0 == 1
test_demo.py:7: AssertionError
___________________________________________________________________________________ test_pytest_assume[1-1] ___________________________________________________________________________________
tp = <class 'pytest_assume.plugin.FailedAssumption'>, value = None, tb = None
def reraise(tp, value, tb=None):
try:
if value is None:
value = tp()
if value.__traceback__ is not tb:
> raise value.with_traceback(tb)
E pytest_assume.plugin.FailedAssumption:
E 1 Failed Assumptions:
E
E test_demo.py:15: AssumptionFailure
E >> pytest.assume(False)
E AssertionError: assert False （前两个断言成功，第三个断言失败了）
/Library/Developer/CommandLineTools/Library/Frameworks/Python3.framework/Versions/3.8/lib/python3.8/site-packages/six.py:702: FailedAssumption
---------------------------------------------------------------------------------- Captured stdout teardown -----------------------------------------------------------------------------------
F
___________________________________________________________________________________ test_pytest_assume[1-0] ___________________________________________________________________________________
tp = <class 'pytest_assume.plugin.FailedAssumption'>, value = None, tb = None
def reraise(tp, value, tb=None):
try:
if value is None:
value = tp()
if value.__traceback__ is not tb:
> raise value.with_traceback(tb)
E pytest_assume.plugin.FailedAssumption:
E 2 Failed Assumptions:
E
E test_demo.py:13: AssumptionFailure
E >> pytest.assume(x == y) （第一个断言失败，后续继续执行）
E AssertionError: assert False
E
E test_demo.py:15: AssumptionFailure
E >> pytest.assume(False)
E AssertionError: assert False
/Library/Developer/CommandLineTools/Library/Frameworks/Python3.framework/Versions/3.8/lib/python3.8/site-packages/six.py:702: FailedAssumption
---------------------------------------------------------------------------------- Captured stdout teardown -----------------------------------------------------------------------------------
F
___________________________________________________________________________________ test_pytest_assume[0-1] ___________________________________________________________________________________
tp = <class 'pytest_assume.plugin.FailedAssumption'>, value = None, tb = None
def reraise(tp, value, tb=None):
try:
if value is None:
value = tp()
if value.__traceback__ is not tb:
> raise value.with_traceback(tb)
E pytest_assume.plugin.FailedAssumption:
E 2 Failed Assumptions:
E
E test_demo.py:13: AssumptionFailure
E >> pytest.assume(x == y) （第一个断言失败，后续继续执行）
E AssertionError: assert False
E
E test_demo.py:15: AssumptionFailure
E >> pytest.assume(False)
E AssertionError: assert False
/Library/Developer/CommandLineTools/Library/Frameworks/Python3.framework/Versions/3.8/lib/python3.8/site-packages/six.py:702: FailedAssumption
---------------------------------------------------------------------------------- Captured stdout teardown -----------------------------------------------------------------------------------
F
=================================================================================== short test summary info ===================================================================================
FAILED test_demo.py::test_simple_assume[1-1] - assert False
FAILED test_demo.py::test_simple_assume[1-0] - assert 1 == 0
FAILED test_demo.py::test_simple_assume[0-1] - assert 0 == 1
FAILED test_demo.py::test_pytest_assume[1-1] - pytest_assume.plugin.FailedAssumption:
FAILED test_demo.py::test_pytest_assume[1-0] - pytest_assume.plugin.FailedAssumption:
FAILED test_demo.py::test_pytest_assume[0-1] - pytest_assume.plugin.FailedAssumption:
====================================================================================== 6 failed in 0.19s ======================================================================================
这里我们可以看出二者的区别了，执行差异如下：
2. 通过上下文管理器with使用pytest-assume
#!/usr/bin/env python3#!coding:utf-8
import pytest
from pytest import assume
@pytest.mark.parametrize(('x', 'y'), [(1, 1), (1, 0), (0, 1)])
def test_simple_assume(x, y): # 使用上下文管理器的好处是不用显示去try和finally捕获异常，建议使用这种写法，简洁有效。
with assume: assert x == y
with assume: assert True
with assume: assert False
主要注意的是，如果上下文管理器里面包含多个断言，则只有第一个会被执行，如
#!/usr/bin/env python3
# !coding:utf-8
import pytest
from pytest import assume
@pytest.mark.parametrize(('x', 'y'), [(1, 1), (1, 0), (0, 1)])
def test_simple_assume(x, y):
# 使用上下文管理器的好处是不用显示去try和finally捕获异常，建议使用这种写法，简洁有效。
with assume:
# 只有第一个断言会被执行！
assert x == y
assert True
assert False
