最近看了许多Pytest的文档，发现有些已经是很早以前的版本了。沿着学习的道路，我记录下我学习Pytest的过程
安装
pip install pytest
安装很简单，如果第一次安装用上述pip安装，如果已经安装了使用
pip install -U pytest
-U参数具有更新作用
我的使用环境
platform win32 -- Python 3.8.10, pytest-6.2.4, py-1.10.0, pluggy-0.13.1
创建第一个测试
用四行代码创建一个简单的测试函数：
# content of test_sample.py def func(x): return x + 1 def test_answer(): assert func(3) == 5
执行
$ pytest =========================== test session starts ============================ platform linux -- Python 3.x.y, pytest-6.x.y, py-1.x.y, pluggy-0.x.y cachedir: $PYTHON_PREFIX/.pytest_cache rootdir: $REGENDOC_TMPDIR collected 1 item test_sample.py F [100%] ================================= FAILURES ================================= _______________________________ test_answer ________________________________ def test_answer(): > assert func(3) == 5 E assert 4 == 5 E + where 4 = func(3) test_sample.py:6: AssertionError ========================= short test summary info ========================== FAILED test_sample.py::test_answer - assert 4 == 5 ============================ 1 failed in 0.12s =============================
这里是在cmd中执行的，也可以在pycharm的Terminal执行（如果你安装了虚拟环境）
这个 [100%] 指运行所有测试用例的总体进度。完成后，pytest会显示一个失败报告，因为 func(3) 不返 5 。
pytest可以搜索指定目录下包括子目录的test_*.py和*_test.py脚本。注意：这里是“.py”文件
断言
pytest 允许您使用标准的python assert 用于验证Python测试中的期望和值
# content of test_assert1.py def f(): return 3 def test_function(): assert f() == 4
断言函数返回某个值。如果此断言失败，您将看到函数调用的返回值：
$ pytest test_assert1.py =========================== test session starts ============================ platform linux -- Python 3.x.y, pytest-6.x.y, py-1.x.y, pluggy-0.x.y cachedir: $PYTHON_PREFIX/.pytest_cache rootdir: $REGENDOC_TMPDIR collected 1 item test_assert1.py F [100%] ================================= FAILURES ================================= ______________________________ test_function _______________________________ def test_function(): > assert f() == 4 E assert 3 == 4 E + where 3 = f() test_assert1.py:6: AssertionError ========================= short test summary info ========================== FAILED test_assert1.py::test_function - assert 3 == 4 ============================ 1 failed in 0.12s =============================
pytest 支持显示最常见的子表达式的值，包括调用、属性、比较以及二进制和一元运算符。
def test_ne(): a = 7 assert a % 2 == 0, "value was odd, should be even"
pytest运行结果
==================================================================================== FAILURES ===================================================================================== _____________________________________________________________________________________ test_ne _____________________________________________________________________________________ def test_ne(): a = 7 > assert a % 2 == 0, "value was odd, should be even" E AssertionError: value was odd, should be even E assert (7 % 2) == 0 2_test.py:10: AssertionError
如图你只是知道7%2==0失败，但7%2的值你不知道。
改为：
def test_ne(): a = 7 value = a % 2 assert value == 0, "value was odd, should be even"
这样会得出：
_____________________________________________________________________________________ test_ne _____________________________________________________________________________________ def test_ne(): a = 7 value = a % 2 > assert value == 0, "value was odd, should be even" E AssertionError: value was odd, should be even E assert 1 == 0 2_test.py:11: AssertionError
这样就会知道value的值，会帮助我们发现问题
关于预期异常的断言
import pytest def test_zero_division(): with pytest.raises(ZeroDivisionError): 1 / 0
如果您需要访问实际的异常信息，可以使用：
def test_recursion_depth(): with pytest.raises(RuntimeError) as excinfo: def f(): f() f() assert "maximum recursion" in str(excinfo.value)
在一个类中分组多个测试
# content of test_class_demo.py class TestClassDemoInstance: value = 0 def test_one(self): self.value = 1 assert self.value == 1 def test_two(self): assert self.value == 1
测试结果：
$ pytest -k TestClassDemoInstance -q .F [100%] ================================= FAILURES ================================= ______________________ TestClassDemoInstance.test_two ______________________ self = <test_class_demo.TestClassDemoInstance object at 0xdeadbeef> def test_two(self): > assert self.value == 1 E assert 0 == 1 E + where 0 = <test_class_demo.TestClassDemoInstance object at 0xdeadbeef>.value test_class_demo.py:9: AssertionError ========================= short test summary info ========================== FAILED test_class_demo.py::TestClassDemoInstance::test_two - assert 0 == 1 1 failed, 1 passed in 0.04s
可见test_one测试成功，test_two测试失败。在这里需注意：在类内对测试进行分组时，每个测试都有一个唯一的类实例。也就是说test_one并没有改变test_two测试实例中value的值。