python单元测试

单元测试

定义

单元测试是指一个自动化的测试：

• 用来验证一小段代码的正确性
• 可以快速执行
• 在独立的环境中执行

断言函数

assertEqual
assertNotEqual
assertTrue
assertFalse
assertIs
assertIsNot
assertIsNone
assertIsNotNone
assertIn
assertNotIn
assertIsInstance
assertNotIsInstance
assertRaises

示例一：assertEqual

class Calculator:def add(self, *args):ret = 0for item in args:ret += itemreturn ret

from unittest import TestCasefrom server.app import Calculatorclass TestCalculator(TestCase):def test_add(self):calculator = Calculator()expect_result = 10actual_result = calculator.add(1, 2, 3, 4)self.assertEqual(expect_result, actual_result)

示例二：assertRaises

class Service:def download_img(self, url: str):if url:return Trueraise ValueError("url error")

from unittest import TestCase
from server.app import Serviceclass TestService(TestCase):def test_download_img_success(self):service = Service()ret = service.download_img("http://www.baidu.com/1.png")self.assertTrue(ret)def test_download_img_with_exception(self):service = Service()with self.assertRaises(ValueError):service.download_img("")

Test Fixtures

在测试方法执行之前或者之后执行的函数或者方法被称为Test Fixtures

• module级别的Fixtures：setUpModule,tearDownModule
• class级别的Fixtures：setUpClass,tearDownClass
• method级别的Fixtures：setUp,tearDown

class Service:def download_img(self, url: str):if url:return Trueraise ValueError("url error")

from unittest import TestCase
from server.app import Servicedef setUpModule():print("执行module前...")def tearDownModule():print("执行module后...")class TestService(TestCase):@classmethoddef setUpClass(cls):print("执行class前...")@classmethoddef tearDownClass(cls):print("执行class后...")def setUp(self):self.service = Service()print("执行任意测试方法前...")def tearDown(self):print("执行任意测试方法后...")def test_download_img_success(self):ret = self.service.download_img("http://www.baidu.com/1.png")self.assertTrue(ret)def test_download_img_with_exception(self):with self.assertRaises(ValueError):self.service.download_img("")

执行module前...
执行class前...
执行任意测试方法前...
执行任意测试方法后...
执行任意测试方法前...
执行任意测试方法后...
执行class后...
执行module后...

Mock

模拟函数，方法，类的行为。

• Mock：主要模拟指定的方法和属性

• MagicMock：Mock的子类，同时模拟了很多Magic方法（__len__，__str__方法等）

示例一：

from unittest.mock import Mockdef test_hello():hello = Mock()hello.find_user.return_value = {'name': '旺财','age': 1}print(hello.find_user())if __name__ == '__main__':test_hello()

{'name': '旺财', 'age': 1}

示例二：

class Student:def __init__(self, id: int, name: str):self.id = idself.name = namedef find_name_by_id(id):passdef save_student(student):passdef chang_name(id: int, new_name: str):student = find_name_by_id(id)if student:student.name = new_namesave_student(student)

from unittest.mock import Mock
from unittest import TestCase
from server.app import chang_name
from server import appclass TestService(TestCase):def test_change_name_with_record(self):service.find_name_by_id = Mock()student = Mock(id=1, name='旧名字')service.find_name_by_id.return_value = studentservice.save_student = Mock()chang_name(1, '新名字')self.assertEqual('新名字', student.name)service.find_name_by_id.assert_called()service.save_student.assert_called()def test_change_name_without_record(self):service.find_name_by_id = Mock()service.find_name_by_id.return_value = Noneservice.save_student = Mock()chang_name(1, '新名字')# 断言没有被调用service.save_student.assert_not_called()

patch

path可以临时用Mock对象替换一个目标（函数，方法，类）。本质还是上一节的Mock操作。

path可以替换的目标：

• 目标必须是可import的
• 是在使用的目标的地方替换而不是替换定义

path的使用方式：

• 装饰器的方式
• 上下文管理器的方式
• 手动方式

装饰器模拟（首选）

class Student:def __init__(self, id: int, name: str):self.id = idself.name = namedef find_name_by_id(id):passdef save_student(student):passdef chang_name(id: int, new_name: str):student = find_name_by_id(id)if student:student.name = new_namesave_student(student)

from unittest.mock import Mock, patch
from unittest import TestCase
from server.app import chang_nameclass TestService(TestCase):@patch("server.server.save_student")@patch("server.server.find_name_by_id")def test_change_name_decorator(self, find_name_by_id_mock, save_student_mock):student = Mock(id=1, name='旧名字')find_name_by_id_mock.return_value = studentchang_name(1, '新名字')self.assertEqual('新名字', student.name)find_name_by_id_mock.assert_called()save_student_mock.assert_called()

上下文管理器模拟

from unittest.mock import Mock, patch
from unittest import TestCase
from server.app import chang_nameclass TestService(TestCase):def test_change_name_context(self):student = Mock(id=1, name='旧名字')with patch("server.server.find_name_by_id") as find_name_by_id_mock, patch("server.server.save_student"):find_name_by_id_mock.return_value = studentchang_name(1, '新名字')self.assertEqual('新名字', student.name)

手动模拟

from unittest.mock import Mock, patch
from unittest import TestCase
from server.app import chang_nameclass TestService(TestCase):@patch("server.server.find_name_by_id")def test_change_name_manual(self, find_name_by_id_mock):student = Mock(id=1, name='旧名字')find_name_by_id_mock.return_value = studentpather = patch("server.server.save_student")pather.start()chang_name(1, '新名字')pather.start()self.assertEqual('新名字', student.name)

测试实例

path里面的模拟对象已经对所有魔术方法都进行了mock，如果不关心返回值可以不用后续return_value了

import os.path
from urllib.request import urlopen, Requestdef download_img(url: str):site_url = Request(url, headers={"User-Agent": "Mozilla/5.0"})with urlopen(site_url) as web_file:img_data = web_file.read()if not img_data:raise Exception(f"Error: cannot load the image from {url}")file_name = os.path.basename(url)with open(file_name, 'wb') as file:file.write(img_data)return f"Download image successfully, {file_name}"

from unittest.mock import patch, MagicMock
from unittest import TestCase
from server.app import download_img# https://www.bilibili.com/video/BV1EK411B7LX/?spm_id_from=333.788&vd_source=35b478ef20f153fb3c729ee792cdf651
class TestService(TestCase):# urlopen在方法参数中被mock为urlopen_mock# urlopen_mock的返回值是一个urlopen_result_mock# urlopen_result_mock的__enter__方法返回值是一个web_file_mock# web_file_mock的read方法返回值需要定义@patch("server.server.urlopen")# 因为在service.service文件中引入了，所以可以直接使用service.service引入Request@patch("server.server.Request.__new__")def test_download_img_with_exception(self, request_init_mock, urlopen_mock):# Setupurl = 'https://www.google.com/a.png'urlopen_result_mock = MagicMock()web_file_mock = MagicMock()urlopen_mock.return_value = urlopen_result_mockurlopen_result_mock.__enter__.return_value = web_file_mockweb_file_mock.read.return_value = Nonewith self.assertRaises(Exception):download_img(url)@patch("builtins.open")@patch("os.path.basename")@patch("server.server.urlopen")@patch("server.server.Request.__new__")def test_download_img_with_success(self, request_init_mock, urlopen_mock, basename_mock, open_mock):# Setupurl = 'https://www.google.com/a.png'urlopen_result_mock = MagicMock()web_file_mock = MagicMock()urlopen_mock.return_value = urlopen_result_mockurlopen_result_mock.__enter__.return_value = web_file_mockweb_file_mock.read.return_value = 'not none'basename_mock.return_value = 'fff'ret = download_img(url)self.assertEqual("Download image successfully, fff", ret)

测试覆盖率

#统计测试覆盖率
python -m coverage run -m unittest#查看覆盖率报告
python -m coverage report#生成html格式的覆盖率报告
python -m coverage html

pytest框架

起步

pytest是一个基于python语言的第三方测试框架。

有以下优点：

• 语法简单
• 自动检测测试代码
• 跳过指定测试
• 开源

安装使用

#安装
pip install pytest#运行(自动查找test_*.py,*_test.py测试文件。自动查找测试文件中test_开头的函数和Test开头的类中的test_开头的方法)
pytest
pytest -v#测试指定测试类
pytest test_xxx.py

常用参数

-v 输出详细的执行信息，比如文件和用例名称
-s 输出调试信息，比如print的打印信息
-x 遇到错误用例立即停止

跳过测试

@pytest.mark.skip
@pytest.mark.skipif

import sysfrom server.app import Student
import pytestdef skip():return sys.platform.casefold() == 'win32'.casefold()# @pytest.mark.skip(reason="暂时跳过")
@pytest.mark.skipif(condition=skip(), reason="window平台跳过")
class TestStudent:def test_student_create(self):student = Student(1, 'bob')assert student.id == 1assert student.name == 'bob'def test_student_create():student = Student(2, 'alice')assert student.id == 2assert student.name == 'alice'

@pytest.fixture

class Student():def __init__(self, id: int, name: str):self.id = idself.name = namedef valid_name(self):if self.name:return 3 < len(self.name) < 10return False

from server.app import Student
import pytest@pytest.fixture
def valid_student():student = Student(1, 'Kite')yield student@pytest.fixture
def not_valid_student1():student = Student(2, 'abcdefjijklmnopq')yield student@pytest.fixture
def not_valid_student2(not_valid_student1):# 这里不能对valid_student的name进行赋值修改哟student = Student(3, 'Bob')student.name = not_valid_student1.nameyield studentdef test_student(valid_student, not_valid_student1, not_valid_student2):ret = valid_student.valid_name()assert retret = not_valid_student1.valid_name()assert not retret = not_valid_student2.valid_name()assert not ret

conftest.py

作用：使得fixture可以被多个文件中的测试用例复用。

在tests目录下建立conftest.py文件，这里引入其他文件中的fixture，那么其他用例中就可以使用这些fixture，你也可以定义fixture在这个文件中（但是不推荐哈）

参数化测试

# 判断是否是奇数
def is_odd(x: int):return x % 2 != 0

import pytestfrom server.app import is_odd@pytest.mark.parametrize("num,expect_ret", [(1, True), (2, False)])
def test_is_odd(num, expect_ret):actual_ret = is_odd(num)assert expect_ret == actual_ret

数据库查询的mock

import pytest
from unittest.mock import patch, MagicMock
from server.controller.message_controller import create_user@pytest.fixture
def mock_session_scope():with patch("server.db.session.session_scope") as mock_session_scope:mock_session_scope_return_value = MagicMock()mock_session_scope.return_value = mock_session_scope_return_valuesession_mock = MagicMock()mock_session_scope_return_value.__enter__.return_value = session_mockyield session_mockdef test_create_user(mock_session_scope):ret = create_user("alice")assert 'ok' == retdef test_create_user_exception(mock_session_scope):with pytest.raises(ValueError):create_user("")

覆盖率

pip install pytest
pip install pytest-cov
pytest --cov --cov-report=html