Pytest -- fixture 简单应用

Fixture

以下命令可以列出所有可用的fixture，包括内置的、插件中的、以及当前项目定义的。

pytest --fixtures

1. fixture作为函数参数
   测试用例可以接受一个fixture函数作为参数（函数命名），fixture函数的注册通过@pytest. fixture来标记，下面看一个简单的例子：
   # test_sample.py

   import pytest
   
   
   @pytest.fixture
   def data():
       return [1, 2, 3]
   
   def test_equal(data):
       print data[0]
       assert data[0] == 1
   

   test_equal需要data的值，pytest将会查找并调用@pytest. fixture标记的data函数，运行将会看到如下结果：
   

2. 共享fixture函数
   上面的一个例子fixture函数只运用于单个py文件，如果想要共享数据函数怎么办呢？只需要将这些fixture函数放入到 conftest.py文件中即可（名称不可变）；在当前路径创建 conftest.py文件，输入以下代码：
   # conftest.py

   	import pytest
   	
   	
   	@pytest.fixture
   	def data():
   	    return [1, 2, 3]
   

   test_sample.py更新代码：

   # test_sample.py

   	import pytest
   	
   	def test_equal(data):
   	    print data[0]
   	    assert data[0] == 1
   

   运行代码将会得到同样的结果；如果此时在test_sample.py文件中也包含fixture标记过的data函数（返回数据改变），那么将会重载该数据（即会调用当前文件中的data）

3. pytest.fixture 特性实现pytest中的setup/teardown
   经典的xunit风格的setUp、tearDown参考：上篇博客和官网介绍。
   pytest.fixture 特性实现：
   这里的scope支持 function, class, module, package or session四种，默认情况下的scope是function。

   • function作用于函数（类中或模块中）
   • class开始于类的始末
   • module开始于模块的始末
   • package/session开始于测试用例的始末（整个包）

   默认使用return的时候是没有tearDown的，但是可以使用yield 、addfinalizer函数来实现tearDown功能。
   具体请参考：

   tests
   │-- conftest.py
   │-- test_sample.py  
   │-- test_sample1.py   
   

   conftest.py代码：

   import pytest
   
   
   pytest.fixture(scope="module")
   def try_module():
       print "#######################module begin####################"
       yield [6, 7, 8]
       print "#######################module end####################"
   
   
   @pytest.fixture()  # 不加(scope="function")默认scope就是function
   def try_function():
       print "#######################function begin####################"
       yield "just a test about function scope"
       print "#######################function end####################"
   
   
   @pytest.fixture(scope="class")
   def try_class(request):
       print "#######################class begin####################"
       def end():
           print "#######################class end####################"
       request.addfinalizer(end)
       return "just a test about class scope"
   
   
   @pytest.fixture(scope="package")  # session == package
   def try_session(request):
       print "#######################session begin####################"
       def end():
           print "#######################session end####################"
       request.addfinalizer(end)
       return "just a test about session scope"
   

   test_sample.py代码：

   class TestAdd(object):
   
       def test1(self, try_session):
           print "test1 something"
           assert 4 == 4
   
       def test2(self, try_module):
           print "test2 something"
           assert 5 == 5
   
       def test3(self, try_class):
           print "test3 something"
           assert 5 == 5
   
       def test4(self, try_function):
           print "test4 something"
           assert 5 == 5
   
       def test5(self):
           print "test5 something"
           assert 5 == 5
   

   test_sample1.py代码：

   def test_file2_1(try_module):
       print "test_file2_1 something"
       assert 2 == 2
   
   
   def test_file2_2(try_function):
       print "test_file2_2 something"
       assert "a"*3 == "aaa"
   
   
   def test_file2_3(try_session):
       print "test_file2_3 something"
       assert "a"*3 == "aaa"
   
   
   def test_file2_4():
       print "test_file2_4 something"
       assert "a"*3 == "aaa"
   
   
   def test_file2_5(try_function):
       print "test_file2_5 something"
       assert "a"*3 == "aaa"
   

   命令行运行：pytest -v -s -q
   运行结果：

   ============================= test session starts =============================
   platform win32 -- Python 2.7.15, pytest-4.5.0, py-1.8.0, pluggy-0.11.0
   rootdir: C:\diy\old coding\test\locust demo\pytest
   collected 10 items 
                                                               
   test_sample.py #######################session begin####################
   test1 something
   .#######################module begin####################
   test2 something
   .#######################class begin####################
   test3 something
   .#######################function begin####################
   test4 something
   .#######################function end####################
   test5 something
   .#######################class end####################
   #######################module end####################
   
   test_sample1.py #######################module begin####################
   test_file2_1 something
   .#######################function begin####################
   test_file2_2 something
   .#######################function end####################
   test_file2_3 something
   .test_file2_4 something
   .#######################function begin####################
   test_file2_2 something
   .#######################function end####################
   #######################module end####################
   #######################session end####################
   
   ========================== 10 passed in 0.16 seconds ==========================
   

   简单应用：

   import time
   import pytest
   from selenium import webdriver
   from selenium.webdriver.common.by import By
   from utils.log import logger
   from utils.config import get_url
   
   @pytest.fixture()
   def chrome_driver(scope="function"):
       print("setup() begin")
       driver = webdriver.Chrome()
       driver.get(get_url())
       print("setup() end")
       yield driver 
       #test_函数结束后，会回到这里，关闭浏览器
       print("teardown() begin")
       driver.close()
       print("teardown() end")
   
   
   class TestBaiDu(object):
   
       locator_kw = (By.ID, 'kw')
       locator_su = (By.ID, 'su')
       locator_result = (By.XPATH, '//div[contains(@class, "result")]/h3/a')
   
       def test_search_0(self, chrome_driver):
           chrome_driver.find_element(*self.locator_kw).send_keys(u'selenium 测试')
           chrome_driver.find_element(*self.locator_su).click()
           time.sleep(2)
           links = chrome_driver.find_elements(*self.locator_result)
           for link in links:
               logger.info(link.text)
   

4. 调用fixture的三种方式

   • 通过传参的方式调用（即上边例子中的用法）
   • 通过usefixtures decorator调用（pytest.mark.usefixtures()标记用例）
   • 通过autouse调用

   usefixtures decorator调用例子：

   test_fixture
   │-- conftest.py
   │-- test_example.py   
   

   conftest.py代码：

   	import pytest
   	@pytest.fixture()  # 不加(scope="function")默认scope就是function
   	def before_function():
   	    print "#######################function begin####################"
   	    yield "just a test about function scope"
   	    print "#######################function end####################"
   
   
   	@pytest.fixture(scope="class")
   	def before_class(request):
   	    print "#######################class begin####################"
   	
   	    def end():
   	        print "#######################class end####################"
   	
   	    request.addfinalizer(end)
   	    return "just a test about class scope"
   

   test_example.py 代码：

   import pytest
   
   
   @pytest.mark.usefixtures("before_function")
   def test_1():
       print('test_1()')
   
   
   @pytest.mark.usefixtures("before_function")
   def test_2():
       print('test_2()')
   
   
   class TestExample(object):
       @pytest.mark.usefixtures("before_function")
       def test_1(self):
           print('test_1()')
   
       @pytest.mark.usefixtures("before_function")
       def test_2(self):
           print('test_2()')
   
   
   @pytest.mark.usefixtures("before_function")
   @pytest.mark.usefixtures("before_class")
   class TestExample1(object):
       # @pytest.mark.usefixtures("before_class")
       def test_1(self):
           print('test_1()')
   
       def test_2(self):
           print('test_2()')
   

   运行pytest -v -s test_example.py输出结果：

   ============================= test session starts =============================
   platform win32 -- Python 2.7.15, pytest-4.5.0, py-1.8.0, pluggy-0.11.0 -- c:\python27\python.exe
   cachedir: .pytest_cache
   rootdir: C:\diy\old coding\test\locust demo\pytest
   collected 6 items                                                              
   
   test_fixture/test_example.py::test_1 #######################function begin####################
   test_1()
   PASSED#######################function end####################
   
   test_fixture/test_example.py::test_2 #######################function begin####################
   test_2()
   PASSED#######################function end####################
   
   test_fixture/test_example.py::TestExample::test_1 #######################function begin####################
   test_1()
   PASSED#######################function end####################
   
   test_fixture/test_example.py::TestExample::test_2 #######################function begin####################
   test_2()
   PASSED#######################function end####################
   
   test_fixture/test_example.py::TestExample1::test_1 #######################class begin####################
   #######################function begin####################
   test_1()
   PASSED#######################function end####################
   
   test_fixture/test_example.py::TestExample1::test_2 #######################function begin####################
   test_2()
   PASSED#######################function end####################
   #######################class end####################
   
   
   ========================== 6 passed in 0.19 seconds ===========================
   

   autouse调用例子：
   当管理用例比较多的时候，这种方法比较方便高效，但是用该功能时也要小心，一定要注意fixture的作用范围。需要注意的是，当使用这种方式时，就不能使用返回值的功了。autouse默认设置为False。当默认为False，就可以选择用上面两种方式来试用fixture。当设置为True时，所有的test都会自动调用这个fixture。autouse遵循scope="关键字参数"规则：当scope="session"时，无论怎样定义只运行一次；当scope="module"时，每个py文件只运行一次；当scope="class"时，每个class只运行一次（但是一个文件中包括function和class时，会在每个function(不在class中)运行一次）；当scope="function"时，每个function运行一次；
   目录结构：

   test_fixture
   │-- conftest.py
   │-- test_autouse.py   
   

   conftest.py代码：

   # coding=utf-8
   import pytest
   
   
   @pytest.fixture(scope="module", autouse=True)
   def before_module():
       print "#######################module begin####################"
       yield [6, 7, 8]
       print "#######################module end####################"
   
   
   @pytest.fixture(autouse=True)  # 不加(scope="function")默认scope就是function
   def before_function():
       print "#######################function begin####################"
       yield "just a test about function scope"
       print "#######################function end####################"
   
   
   @pytest.fixture(scope="class",autouse=True)
   def before_class(request):
       print "#######################class begin####################"
   
       def end():
           print "#######################class end####################"
   
       request.addfinalizer(end)
       return "just a test about class scope"
   
   
   @pytest.fixture(scope="package",autouse=True)  # session == package
   def before_package(request):
       print "#######################session begin####################"
   
       def end():
           print "#######################session end####################"
   
       request.addfinalizer(end)
       return "just a test about session scope"
   

   test_autouse.py代码：

    def test_1():
       print('test_1()')
   
   
   def test_2():
       print('test_2()')
   
   
   class TestExample(object):
       def test_1(self):
           print('test_1()')
   
       def test_2(self):
           print('test_2()')
   

   运行pytest -v -s test_autouse.py输出结果：

    ============================= test session starts =============================
   platform win32 -- Python 2.7.15, pytest-4.5.0, py-1.8.0, pluggy-0.11.0 -- c:\python27\python.exe
   cachedir: .pytest_cache
   rootdir: C:\diy\old coding\test\locust demo\pytest
   collected 4 items                                                              
   
   test_fixture/test_autouse.py::test_1 #######################session begin####################
   #######################module begin####################
   #######################class begin####################
   #######################function begin####################
   test_1()
   PASSED#######################function end####################
   #######################class end####################
   
   test_fixture/test_autouse.py::test_2 #######################class begin####################
   #######################function begin####################
   test_2()
   PASSED#######################function end####################
   #######################class end####################
   
   test_fixture/test_autouse.py::TestExample::test_1 #######################class begin####################
   #######################function begin####################
   test_1()
   PASSED#######################function end####################
   
   test_fixture/test_autouse.py::TestExample::test_2 #######################function begin####################
   test_2()
   PASSED#######################function end####################
   #######################class end####################
   #######################module end####################
   #######################session end####################
   
   
   ========================== 4 passed in 0.11 seconds ===========================
   

   fixture中使用fixture（test_something.py）：

   	import pytest
   	@pytest.fixture(scope="module")
   def foo(request):
       print('\nfoo setup - module fixture')
       def fin():
           print('foo teardown - module fixture')
       request.addfinalizer(fin)
    
   @pytest.fixture()
   def bar(request, foo):
       print('bar setup - function fixture')
       def fin():
           print('bar teardown - function fixture')
       request.addfinalizer(fin)
    
   @pytest.fixture()
   def baz(request, bar):
       print('baz setup - function fixture')
       def fin():
           print('baz teardown - function fixture')
       request.addfinalizer(fin)
    
   def test_one(baz):
       print('in test_one()')
    
   def test_two(bar): # only use bar
       print('in test_two()')
   

   运行py.test -s test_something.py，输出：

   ============================= test session starts =============================
   platform win32 -- Python 2.7.2 -- pytest-2.4.2
   collected 2 items
    
   test_modular.py
   foo setup - module fixture
   bar setup - function fixture
   baz setup - function fixture
   in test_one()
   .baz teardown - function fixture
   bar teardown - function fixture
   bar setup - function fixture
   in test_two()
   .bar teardown - function fixture
   foo teardown - module fixture
    
   ========================== 2 passed in 0.02 seconds ===========================
   

5. 参数化
   利用fixture的params参数进行参数化：

   @pytest.fixture(params=[0, 1, 3])
   def c_set(request):
       temp = request.param
       yield temp
   
   
   def test_c(c_set):
       assert c_set == 3
   

   上面例子运行了三个测试用例，运行结果：

   	============================= test session starts =============================
   platform win32 -- Python 2.7.15, pytest-4.5.0, py-1.8.0, pluggy-0.11.0 -- c:\python27\python.exe
   cachedir: .pytest_cache
   rootdir: C:\diy\old coding\test\locust demo\pytest
   collected 3 items                                                              
   
   test_parametrizing.py::test_c[0] FAILED
   test_parametrizing.py::test_c[1] FAILED
   test_parametrizing.py::test_c[3] PASSED
   
   ================================== FAILURES ===================================
   __________________________________ test_c[0] __________________________________
   
   c_set = 0
   
       def test_c(c_set):
   >       assert c_set == 3
   E       assert 0 == 3
   E         -0
   E         +3
   
   test_parametrizing.py:50: AssertionError
   __________________________________ test_c[1] __________________________________
   
   c_set = 1
   
       def test_c(c_set):
   >       assert c_set == 3
   E       assert 1 == 3
   E         -1
   E         +3
   
   test_parametrizing.py:50: AssertionError
   ===================== 2 failed, 1 passed in 0.18 seconds ======================
   
   

   也可以利用ids参数对每个测试定制一个名称标志，将上边函数加一个ids参数，可以用–collect-only参数来查看（pytest --collect-only test_parametrizing.py），添加的ids参数可以用-k来过滤运行指定参数的方法（pytest -k "apple" test_parametrizing.py只会运行参数params=[0, 1, 3]中值为1的，运行一次），代码如下：

   @pytest.fixture(params=[0, 1, 3], ids=["apple","banana","orange"])
   def c_set(request):
       temp = request.param
       yield temp
   
   
   def test_c(c_set):
       assert c_set == 3
   

   也可以为ids传递函数作为参数：

   def idfn(fixture_value): 
       if fixture_value == 0: 
           return "eggs" 
       else: 
           return None
   
   
   @pytest.fixture(params=[0, 1], ids=idfn) 
   def d(request): 
       return request.param
   
   
   def test_d(d): 
       pass
   

   使用pytest.param() ，参数值2将被跳过：

   import pytest 
   @pytest.fixture(params=[0, 1, pytest.param(2, marks=pytest.mark.skip)]) 
   def e_set(request): 
       return request.param
   
   
   def test_e(e_set): 
       pass
   

   利用@pytest.mark.parametrize直接对测试函数进行参数化：

   import pytest
   def add(a, b):
       return a + b
   
   @pytest.mark.parametrize("test_input, expected", [
       ([1, 1], 2),
       ([2, 2], 4),
       ([0, 1], 1),
   ])
   def test_add(test_input, expected):
       assert expected == add(test_input[0], test_input[1])
   

6. 不同级别的重写fixture

   • 文件夹级别（conftest.py）重写fixture
   • module级别的重写fixture
   • 直接利用参数重写fixture

   文件夹级别（conftest.py）重写fixture

    tests/ 
   	__init__.py
   	conftest.py # content of tests/conftest.py 
   		import pytest
   		@pytest.fixture 
   		def username(): 
   			return 'username'
   	test_something.py # content of tests/test_something.py 
   		def test_username(username):
   			 assert username == 'username'
   	subfolder/ __init__.py
   		conftest.py # content of tests/subfolder/conftest.py 
   			import pytest
   			@pytest.fixture 
   			def username(username): 
   				return 'overridden-' + username
   		test_something.py # content of tests/subfolder/test_something.py 
   			def test_username(username): 
   				assert username == 'overridden-username'
   

   通过上面的例子可以看到，对于特定的测试文件夹级别，可以覆盖具有相同名称的fixture。注意，重写的fixture可以轻松地访问被重写的base fixture或super fixture
   module级别的重写fixture

    tests/
   	__init__.py
   	conftest.py # content of tests/conftest.py 
   	@pytest.fixture 
   	def username(): 
   		return 'username'
   test_something.py # content of tests/test_something.py 
   	import pytest
   	@pytest.fixture 
   	def username(username): 
   		return 'overridden-' + username
   	def test_username(username): 
   		assert username == 'overridden-username'
   test_something_else.py # content of tests/test_something_else.py 
   	import pytest
   	@pytest.fixture 
   	def username(username): 
   		return 'overridden-else-' + username
   	def test_username(username): 
   		assert username == 'overridden-else-username'
   

   在上面的示例中，在模块级别，相同名称的fixture可以被重写
   直接利用参数重写fixture

   	tests/ __init__.py
   		conftest.py # content of tests/conftest.py 
   			import pytest
   			@pytest.fixture 
   			def username(): 
   				return 'username'
   			@pytest.fixture 
   			def other_username(username):
   				 return 'other-' + username
   		test_something.py # content of tests/test_something.py 
   			import pytest
   			@pytest.mark.parametrize('username', ['directly-overridden-username']) 
   			def test_username(username):
   				 assert username == 'directly-overridden-username'
   			@pytest.mark.parametrize('username', ['directly-overridden-username-other'])
   			 def test_username_other(other_username):
   				  assert other_username == 'other-directly-overridden-username-other'
   

   在上面的例子中，fixture值被test参数值覆盖。请注意，即使测试没有直接使用fixture(在函数原型中没有提到)，fixture的值也可以通过这种方式被覆盖

参考：

• API：https://docs.pytest.org/en/latest/reference.html#initialization-hooks
• skip：https://docs.pytest.org/en/latest/skipping.html
• 样例：https://docs.pytest.org/en/latest/example/
• 自定义测试集合：https://docs.pytest.org/en/latest/example/pythoncollection.html#customizing-test-collection