Pytest-Python单元测试
谭翔
前言論
本文从六个部分总结pytest库的用法和使用场景
一、构造测试用例
如何构造樂
pytest在test*.py 或者 *test.py 文件中; 寻找以 test开头或结尾的函数，以Test开头的类里面的 以 test开头或结尾的方法，将这些作为测试用例。
所以需要满足以下
-
1.文件名以
test开头或结尾； -
2.函数/方法以
test开头； -
3.class类名以
Test开头, 且不能有__init__方法ps: 基于PEP8规定一般我们的测试用例都是 test_xx, 类则以Test_; 即带下划线的，但是要注意的是不要下划线也是可以运行的！
如何运行辰
pytest.main()作为测试用例的入口- 当前目录
pytest.main(["./"]) - 指定目录/模块
pytest.main(["./sub_dir"]) # 运行sub_dir目录 pytest.main(["./sub_dir/test_xx.py"]) # 运行指定模块 - 指定用例
pytest.main(["./sub_dir/test_xx.py::test_func"]) # 运行指定函数用例 pytest.main(["./sub_dir/test_xx.py::TestClass::test_method"]) # 运行指定类用例下的方法 - 参数
其实和pytest命令行参数一样，只是将参数按照顺序放到列表中传参给main函数
- 当前目录
命令行
略(参下 - 以下用例都使用的命令行)
简单目录结构示例
-
目录树
tests
├── test_class.pyclass TestClass: def test_pass(): assert 1 def test_faild(): assert 0└── test_func.py
def test_pass(): assert 1 def test_faild(): assert 0项目目录下会建立一个tests目录，里面存放单元测试用例，如上所示 ,两个文件
test_class.py是测试类，test_func.py是测试函数
在如上目录下运行pytest, pytest会在当前目录及递归子目录下按照上述的规则运行测试用例；
如果只是想收集测试用例，查看收集到哪些测试用例可以查看--collect-only命令选项[python -m] pytest --collect-only输出, 可以看到
collected 3 items即该命令收集到3个测试用例============================================================= test session starts ============================================================== platform darwin -- Python 3.7.3, pytest-4.6.5, py-1.11.0, pluggy-0.13.1 rootdir: /Users/huangxiaonan/PycharmProjects/future plugins: anyio-3.5.0 collected 3 items <Module tests/test_class.py> <Class Test_ABC> <Function test_a> <Function test_b> <Module tests/test_func.py> <Function test_f> ========================================================= no tests ran in 0.15 seconds =========================================================
二、基础用法
使用断言廊
测试用例基础工具assert
- 自定义断言
在contest.py自定义pytest_assertrepr_compare该函数有三个参数- op
- left
- right
test_assert.pyclass Foo: def __init__(self, val): self.val = val def __eq__(self, other): return self.val == other.val def pytest_assertrepr_compare(op, left, right): if isinstance(left, Foo) and isinstance(right, Foo) and op == "==": return [ "Comparing Foo instances:", " vals: {} != {}".format(left.val, right.val), ]
输出from conftest import Foo def test_compare(): f1 = Foo(1) f2 = Foo(2) assert f1 == f2============================================================= test session starts ============================================================== platform darwin -- Python 3.7.3, pytest-4.6.5, py-1.11.0, pluggy-0.13.1 -- /Library/Developer/CommandLineTools/usr/bin/python3 cachedir: .pytest_cache rootdir: /Users/PycharmProjects/future/tests, inifile: pytest.ini plugins: anyio-3.5.0 collected 1 item tests/test_assert.py::test_compare FAILED =================================================================== FAILURES =================================================================== _________________________________________________________________ test_compare _________________________________________________________________ def test_compare(): f1 = Foo(1) f2 = Foo(2) > assert f1 == f2 E assert Comparing Foo instances: E vals: 1 != 2 tests/test_assert.py:7: AssertionError =========================================================== 1 failed in 0.05 seconds ===========================================================
捕获异常類
- 使用
pytest.raises()捕获指定异常，以确定异常发生import pytest def test_raises(): with pytest.raises(TypeError) as e: raise TypeError("TypeError") exec_msg = e.value.args[0] assert exec_msg == 'TypeError'
指定运行测试用例
- 1.命令行
::显示指定pytest test__xx.py::test_func - 2.命令行
-k模糊匹配pytest -k a # 调用所有带a字符的测试用例 - 3.
pytest.mark.自定义标记装饰器做标记- test_mark.py
@pytest.mark.finished def test_func1(): assert 1 == 1 @pytest.mark.unfinished def test_func2(): assert 1 != 1 @pytest.mark.success @pytest.finished def test_func3(): assert 1 == 1 - 注册标记到配置
- 方式1: conftest.py
def pytest_configure(config): marker_list = ["finished", "unfinished", "success"] # 标签名集合 for markers in marker_list: config.addinivalue_line("markers", markers) - 方式2: pytest.ini
[pytest] markers= finished: finish error: error unfinished: unfinished
ps: 如果不注册也可以运行，但是会有 warnning <PytestUnknownMarkWarning> - 方式1: conftest.py
- 运行方式
注意: 标签要用双引号- 运行带
finished标签的用例pytest -m "finished" # - 多选
运行 test_fun1test_fun2pytest -m "finished or unfinished" - 多标签用例
运行 test_fun3pytest -m "finished and success""
- 运行带
- test_mark.py
跳过测试用例 SKIPPED
装饰测试函数或者测试类
pytest.mark.skip(reason="beause xxx")直接跳过pytest.mark.skipif(a>=1, reason="当a>=1执行该测试用例")满足条件跳过- code
import pytest @pytest.mark.skip(reason="no reason, skip") class TestB: def test_a(self): print("------->B test_a") assert 1 def test_b(self): print("------->B test_b") @pytest.mark.skipif(a>=1, reason="当a>=1执行该测试用例") def test_func2(): assert 1 != 1 - 输出 (运行
pytest tests/test_mark.py -v)============================================================= test session starts ============================================================== platform darwin -- Python 3.7.3, pytest-4.6.5, py-1.11.0, pluggy-0.13.1 -- /Library/Developer/CommandLineTools/usr/bin/python3 cachedir: .pytest_cache rootdir: /Users/huangxiaonan/PycharmProjects/future/tests, inifile: pytest.ini plugins: anyio-3.5.0 collected 3 items tests/test_mark.py::TestB::test_a SKIPPED [ 33%] tests/test_mark.py::TestB::test_b SKIPPED [ 66%] tests/test_mark.py::test_func2 SKIPPED [100%] ========================================================== 3 skipped in 0.02 seconds ===========================================================
- code
预见的错误 XPASS
可预见的错误，不想skip, 比如某个测试用例是未来式的(版本升级后)
pytest.mark.xfail(version < 2, reason="no supported until version==2")
参数化
pytest.mark.parametrize(argnames, argvalues)- code
@pytest.mark.parametrize('passwd', ['123456', 'abcdefdfs', 'as52345fasdf4']) def test_passwd_length(passwd): assert len(passwd) >= 8 - 输出
多参数情况============================================================= test session starts ============================================================== platform darwin -- Python 3.7.3, pytest-4.6.5, py-1.11.0, pluggy-0.13.1 -- /Library/Developer/CommandLineTools/usr/bin/python3 cachedir: .pytest_cache rootdir: /Users/huangxiaonan/PycharmProjects/future/tests, inifile: pytest.ini plugins: anyio-3.5.0 collected 3 items tests/test_params.py::test_passwd_length[123456] FAILED [ 33%] tests/test_params.py::test_passwd_length[abcdefdfs] PASSED [ 66%] tests/test_params.py::test_passwd_length[as52345fasdf4] PASSED [100%] =================================================================== FAILURES ===================================================================
@pytest.mark.parametrize('user, passwd', [('jack', 'abcdefgh'), ('tom', 'a123456a')])
三、Fixture
常见的就是数据库的初始连接和最后关闭操作
简单范例
- code
在生产环境中一般定义在@pytest.fixture() def postcode(): return '010' def test_postcode(postcode): assert postcode == '010'conftest.py集中管理；
可以看到如上的范例中定义了一个 fixture 名称以被pytest.fixture()装饰的函数此处为postcode， 如果想要使用它，需要给测试用例添加同名形参；也可以自定义固件名称pytest.fixture(name="code")此时 fixture的名称为code.
预处理和后处理
以yield分割，预处理在yield之前，后处理在yield之后
- code
import pytest @pytest.fixture(scope="module") def db_conn(): print(f"mysql conn") conn = None yield conn print(f"mysql close") del conn def test_postcode(db_conn): print("db_conn = ", db_conn) assert db_conn == None
fixture作用域聾
scope可接受如下参数
- function: 函数级(默认)，每个测试函数都会执行一次固件；
- class: 类级别，每个测试类执行一次，所有方法都可以使用；
- module: 模块级，每个模块执行一次，模块内函数和方法都可使用；
- session: 会话级，一次测试只执行一次，所有被找到的函数和方法都可用。
pytest.mark.usefixtures
装饰类或者函数用例，完成一些用例的预处理和后处理工作
- code
执行import pytest @pytest.fixture(scope="module") def db_conn(): print(f"mysql conn") conn = None yield conn print(f"mysql close") del conn @pytest.fixture(scope="module") def auth(): print(f"login") user = None yield user print(f"logout") del user @pytest.mark.usefixtures("db_conn", "auth") class TestA: def test_a(self): assert 1 def test_b(self): assert 1python3 -m pytest tests/test_fixture.py -vs
以上两个fixture将以 db_conn -> auth 的顺序(即位置参数的先后顺序)在用例TestA构建作用域
另外：也可以多个以多个pytest.mark.usefixtures的方式构建，此时靠近被装饰对象的fixture优先 - 输出
============================================================= test session starts ============================================================== platform darwin -- Python 3.7.3, pytest-4.6.5, py-1.11.0, pluggy-0.13.1 -- /Library/Developer/CommandLineTools/usr/bin/python3 cachedir: .pytest_cache rootdir: /Users/PycharmProjects/future/tests, inifile: pytest.ini plugins: anyio-3.5.0 collected 2 items tests/test_fixture.py::TestA::test_a mysql conn login PASSED tests/test_fixture.py::TestA::test_b PASSEDlogout mysql close =========================================================== 2 passed in 0.06 seconds ===========================================================
fixture自动化
fixture参数autouse=True, 则fixture将自动执行
新建一个conftest.py文件，添加如下代码，以下代码是官方给出的demo，计算 session 作用域(总测试)，及 function 作用域(每个函数/方法)的运行时间
- code
当执行import time import pytest DATE_FORMAT = '%Y-%m-%d %H:%M:%S' @pytest.fixture(scope='session', autouse=True) def timer_session_scope(): start = time.time() print('\nstart: {}'.format(time.strftime(DATE_FORMAT, time.localtime(start)))) yield finished = time.time() print('finished: {}'.format(time.strftime(DATE_FORMAT, time.localtime(finished)))) print('Total time cost: {:.3f}s'.format(finished - start)) @pytest.fixture(autouse=True) def timer_function_scope(): start = time.time() yield print(' Time cost: {:.3f}s'.format(time.time() - start))conftest.py当前目录及递归子目录下的所有用例时将自动执行以上fixture
fixture参数化
区别于参数化测试， 这部分主要是对固件进行参数化，比如连接两个不同的数据库
固件参数化需要使用 pytest 内置的固件 request，并通过 request.param 获取参数。
- code
import pytest @pytest.fixture(params=[ ('redis', '6379'), ('mysql', '3306') ]) def param(request): return request.param @pytest.fixture(autouse=True) def db(param): print('\nSucceed to connect %s:%s' % param) yield print('\nSucceed to close %s:%s' % param) def test_api(): assert 1 == 1 - 输出
============================================================= test session starts ============================================================== platform darwin -- Python 3.7.3, pytest-4.6.5, py-1.11.0, pluggy-0.13.1 -- /Library/Developer/CommandLineTools/usr/bin/python3 cachedir: .pytest_cache rootdir: /Users/PycharmProjects/future/tests, inifile: pytest.ini plugins: anyio-3.5.0 collected 2 items tests/test_fixture.py::test_api[param0] Succeed to connect redis:6379 PASSED Succeed to close redis:6379 tests/test_fixture.py::test_api[param1] Succeed to connect elasticsearch:9200 PASSED Succeed to close elasticsearch:9200 =========================================================== 2 passed in 0.01 seconds ===========================================================
内置fixture瀞
-
tmpdir
作用域function
用于临时文件和目录管理，默认会在测试结束时删除
tmpdir.mkdir()创建目临时目录返回创建的目录句柄，tmpdir.join()创建临时文件返回创建的文件句柄- code
def test_tmpdir(tmpdir): a_dir = tmpdir.mkdir('mytmpdir') a_file = a_dir.join('tmpfile.txt') a_file.write('hello, pytest!') assert a_file.read() == 'hello, pytest!'
- code
-
tmpdir_factory
作用于所有作用域- code
@pytest.fixture(scope='module') def my_tmpdir_factory(tmpdir_factory): a_dir = tmpdir_factory.mktemp('mytmpdir') a_file = a_dir.join('tmpfile.txt') a_file.write('hello, pytest!') return a_file
- code
-
pytestconfig
读取命令行参数和配置文件; 等同于request.config- conftest.py定义
pytest_addoption用于添加命令行参数def pytest_addoption(parser): parser.addoption('--host', action='store', help='host of db') parser.addoption('--port', action='store', default='8888', help='port of db') - test_config.py 定义
def test_option1(pytestconfig): print('host: %s' % pytestconfig.getoption('host')) print('port: %s' % pytestconfig.getoption('port'))
- conftest.py定义
-
capsys
临时关闭标准输出stdout，stderr- code
import sys def test_stdout(capsys): sys.stdout.write("stdout>>") sys.stderr.write("stderr>>") out, err = capsys.readouterr() print(f"capsys stdout={out}") print(f"capsys stderr={err}") - 输出
============================================================= test session starts ============================================================== platform darwin -- Python 3.7.3, pytest-4.6.5, py-1.11.0, pluggy-0.13.1 -- /Library/Developer/CommandLineTools/usr/bin/python3 cachedir: .pytest_cache rootdir: /Users/huangxiaonan/PycharmProjects/future/tests, inifile: pytest.ini plugins: anyio-3.5.0 collected 1 item tests/test_assert.py::test_stdout capsys stdout=stdout>> capsys stderr=stderr>> PASSED =========================================================== 1 passed in 0.05 seconds ===========================================================
- code
-
recwarn
捕获程序中的warnnings告警-
code (不引入recwarn)
import warnings def warn(): warnings.warn('Deprecated function', DeprecationWarning) def test_warn(): warn() -
输出 可以看到有
warnnings summary告警============================================================= test session starts ============================================================== platform darwin -- Python 3.7.3, pytest-4.6.5, py-1.11.0, pluggy-0.13.1 rootdir: /Users/huangxiaonan/PycharmProjects/future/tests, inifile: pytest.ini plugins: anyio-3.5.0 collected 1 item tests/test_assert.py . [100%] =============================================================== warnings summary =============================================================== test_assert.py::test_warn /Users/huangxiaonan/PycharmProjects/future/tests/test_assert.py:5: DeprecationWarning: Deprecated function warnings.warn('Deprecated function', DeprecationWarning) -- Docs: https://docs.pytest.org/en/latest/warnings.html ===================================================== 1 passed, 1 warnings in 0.05 seconds ===================================================== -
code 引入recwarn
import warnings def warn(): warnings.warn('Deprecated function', DeprecationWarning) def test_warn(recwarn): warn()此时将无告警，此时告警对象可在测试用例中通过
recwarn.pop()获取到 -
code 以下方式也可以捕获warn
def test_warn(): with pytest.warns(None) as warnings: warn()
-
-
monkeypatch
按照理解来说这些函数的作用仅仅是在测试用例的作用域内有效，参见setenv- setattr(target, name, value, raising=True)，设置属性；
- delattr(target, name, raising=True)，删除属性；
- setitem(dic, name, value)，字典添加元素；
- delitem(dic, name, raising=True)，字典删除元素；
- setenv(name, value, prepend=None)，设置环境变量；
输出 可以看到import os def test_config_monkeypatch(monkeypatch): monkeypatch.setenv('HOME', "./") import os print(f"monkeypatch: env={os.getenv('HOME')}") def test_config_monkeypat(): import os print(f"env={os.getenv('HOME')}")monkeypath给环境变量大的补丁只在定义的测试用例内部有效============================================================= test session starts ============================================================== platform darwin -- Python 3.7.3, pytest-4.6.5, py-1.11.0, pluggy-0.13.1 -- /Library/Developer/CommandLineTools/usr/bin/python3 cachedir: .pytest_cache rootdir: /Users/huangxiaonan/PycharmProjects/future/tests, inifile: pytest.ini plugins: anyio-3.5.0 collected 2 items tests/test_assert.py::test_config_monkeypatch monkeypatch: env=./ PASSED tests/test_assert.py::test_config_monkeypat env=/Users/huangxiaonan PASSED =========================================================== 2 passed in 0.06 seconds =========================================================== - delenv(name, raising=True)，删除环境变量；
- syspath_prepend(path)，添加系统路径；
- chdir(path)，切换目录。
四、Hooks
五、配置文件⚙️
pytest两类配置文件
- 1.pytest.ini
- 2.conftest.py
六、一个完整的测试用例应该是什么样的？樂
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