Mockito浅谈

2016-07-21 10:00 流水不腐小夏 Share this on Facebook 点击报名

  Mockito简介

  什么是mock?

  在软件开发的世界之外, "mock"一词是指模仿或者效仿。 因此可以将“mock”理解为一个替身,替代者. 在软件开发中提及"mock",通常理解为模拟对象或者Fake。

  为什么需要Mock?

  Mock是为了解决units之间由于耦合而难于被测试的问题。所以mock object是unit test的一部分。

  Mock的好处是什么?

  提前创建测试,TDD(测试驱动开发)

  这是个最大的好处吧。如果你创建了一个Mock那么你就可以在service接口创建之前写Service Tests了,这样你就能在开发过程中把测试添加到你的自动化测试环境中了。换句话说,模拟使你能够使用测试驱动开发。

  团队可以并行工作

  这类似于上面的那点;为不存在的代码创建测试。但前面讲的是开发人员编写测试程序,这里说的是测试团队来创建。当还没有任何东西要测的时候测试团队如何来创建测试呢?模拟并针对模拟测试!这意味着当service借口需要测试时,实际上QA团队已经有了一套完整的测试组件;没有出现一个团队等待另一个团队完成的情况。这使得模拟的效益型尤为突出了。

  你可以创建一个验证或者演示程序。

  由于Mocks非常高效,Mocks可以用来创建一个概念证明,作为一个示意图,或者作为一个你正考虑构建项目的演示程序。这为你决定项目接下来是否要进行提供了有力的基础,但最重要的还是提供了实际的设计决策。

  为无法访问的资源编写测试

  这个好处不属于实际效益的一种,而是作为一个必要时的“救生圈”。有没有遇到这样的情况?当你想要测试一个service接口,但service需要经过防火墙访问,防火墙不能为你打开或者你需要认证才能访问。遇到这样情况时,你可以在你能访问的地方使用MockService替代,这就是一个“救生圈”功能。

  Mock 可以交给用户

  在有些情况下,某种原因你需要允许一些外部来源访问你的测试系统,像合作伙伴或者客户。这些原因导致别人也可以访问你的敏感信息,而你或许只是想允许访问部分测试环境。在这种情况下,如何向合作伙伴或者客户提供一个测试系统来开发或者做测试呢?最简单的就是提供一个mock,无论是来自于你的网络或者客户的网络。soapUI mock非常容易配置,他可以运行在soapUI或者作为一个war包发布到你的java服务器里面。

  隔离系统

  有时,你希望在没有系统其他部分的影响下测试系统单独的一部分。由于其他系统部分会给测试数据造成干扰,影响根据数据收集得到的测试结论。使用mock你可以移除掉除了需要测试部分的系统依赖的模拟。当隔离这些mocks后,mocks就变得非常简单可靠,快速可预见。这为你提供了一个移除了随机行为,有重复模式并且可以监控特殊系统的测试环境。

  Mockito使用示例

  模拟对象

  // 模拟LinkedList 的一个对象

  LinkedList mockedList = mock(LinkedList.class);

  // 此时调用get方法,会返回null,因为还没有对方法调用的返回值做模拟

  System.out.println(mockedList.get(0));

  模拟方法调用的返回值

  // 模拟获取第一个元素时,返回字符串first。 给特定的方法调用返回固定值在官方说法中称为stub。

  when(mockedList.get(0)).thenReturn("first");

  // 此时打印输出first

  System.out.println(mockedList.get(0));

  模拟方法调用抛出异常

  // 模拟获取第二个元素时,抛出RuntimeException

  when(mockedList.get(1)).thenThrow(new RuntimeException());

  // 此时将会抛出RuntimeException

  System.out.println(mockedList.get(1));

  如果一个函数没有返回值类型,那么可以使用此方法模拟异常抛出

  doThrow(new RuntimeException("clear exception")).when(mockedList).clear();

  mockedList.clear();

  模拟调用方法时的参数匹配

  // anyInt()匹配任何int参数,这意味着参数为任意值,其返回值均是element

  when(mockedList.get(anyInt())).thenReturn("element");

  // 此时打印是element

  System.out.println(mockedList.get(999));

  模拟方法调用次数

  // 调用add一次

  mockedList.add("once");

  // 下面两个写法验证效果一样,均验证add方法是否被调用了一次

  verify(mockedList).add("once");

  verify(mockedList, times(1)).add("once");

  校验行为

  // mock creation

  List mockedList = mock(List.class);

  // using mock object

  mockedList.add("one");

  mockedList.clear();

  //verification

  verify(mockedList).add("one");

  verify(mockedList).clear();

  模拟方法调用(Stubbing)

  //You can mock concrete classes, not just interfaces

  LinkedList mockedList = mock(LinkedList.class);

  //stubbing

  when(mockedList.get(0)).thenReturn("first");

  when(mockedList.get(1)).thenThrow(new RuntimeException());

  //following prints "first"

  System.out.println(mockedList.get(0));

  //following throws runtime exception

  System.out.println(mockedList.get(1));

  //following prints "null" because get(999) was not stubbed

  System.out.println(mockedList.get(999));

  verify(mockedList).get(0);

  参数匹配

  //stubbing using built-in anyInt() argument matcher

  when(mockedList.get(anyInt())).thenReturn("element");

  //stubbing using custom matcher (let's say isValid() returns your own matcher implementation):

  when(mockedList.contains(argThat(isValid()))).thenReturn("element");

  //following prints "element"

  System.out.println(mockedList.get(999));

  //you can also verify using an argument matcher

  verify(mockedList).get(anyInt());

  //argument matchers can also be written as Java 8 Lambdas

  verify(mockedList).add(someString -> someString.length() > 5);

  校验方法调用次数

  //using mock

  mockedList.add("once");

  mockedList.add("twice");

  mockedList.add("twice");

  mockedList.add("three times");

  mockedList.add("three times");

  mockedList.add("three times");

  //following two verifications work exactly the same - times(1) is used by default

  verify(mockedList).add("once");

  verify(mockedList, times(1)).add("once");

  //exact number of invocations verification

  verify(mockedList, times(2)).add("twice");

  verify(mockedList, times(3)).add("three times");

  //verification using never(). never() is an alias to times(0)

  verify(mockedList, never()).add("never happened");

  //verification using atLeast()/atMost()

  verify(mockedList, atLeastOnce()).add("three times");

  verify(mockedList, atLeast(2)).add("five times");

  verify(mockedList, atMost(5)).add("three times");

  模拟无返回方法抛出异常

  doThrow(new RuntimeException()).when(mockedList).clear();

  //following throws RuntimeException:

  mockedList.clear();

  校验方法调用顺序

  // A. Single mock whose methods must be invoked in a particular order

  List singleMock = mock(List.class);

  //using a single mock

  singleMock.add("was added first");

  singleMock.add("was added second");

  //create an inOrder verifier for a single mock

  InOrder inOrder = inOrder(singleMock);

  //following will make sure that add is first called with "was added first, then with "was added second"

  inOrder.verify(singleMock).add("was added first");

  inOrder.verify(singleMock).add("was added second");

  // B. Multiple mocks that must be used in a particular order

  List firstMock = mock(List.class);

  List secondMock = mock(List.class);

  //using mocks

  firstMock.add("was called first");

  secondMock.add("was called second");

  //create inOrder object passing any mocks that need to be verified in order

  InOrder inOrder = inOrder(firstMock, secondMock);

  //following will make sure that firstMock was called before secondMock

  inOrder.verify(firstMock).add("was called first");

  inOrder.verify(secondMock).add("was called second");

  // Oh, and A + B can be mixed together at will

  校验方法是否从未调用

  //using mocks - only mockOne is interacted

  mockOne.add("one");

  //ordinary verification

  verify(mockOne).add("one");

  //verify that method was never called on a mock

  verify(mockOne, never()).add("two");

  //verify that other mocks were not interacted

  verifyZeroInteractions(mockTwo, mockThree);

  快速创建Mock对象

  public class ArticleManagerTest {

  @Mock private ArticleCalculator calculator;

  @Mock private ArticleDatabase database;

  @Mock private UserProvider userProvider;

  @Before

  public void before(){

  MockitoAnnotations.initMocks(this);

  }

  }

  自定义返回不同结果

  when(mock.someMethod("some arg"))

  .thenThrow(new RuntimeException()) // 第一次会抛出异常

  .thenReturn("foo"); // 第二次会返回这个结果

  //First call: throws runtime exception:

  mock.someMethod("some arg"); // 第一次

  //Second call: prints "foo"

  System.out.println(mock.someMethod("some arg")); // 第二次

  //Any consecutive call: prints "foo" as well (last stubbing wins).

  System.out.println(mock.someMethod("some arg")); // 第n次(n> 2),依旧以最后返回最后一个配置

  对返回结果进行拦截

  when(mock.someMethod(anyString())).thenAnswer(new Answer() {

  Object answer(InvocationOnMock invocation) {

  Object[] args = invocation.getArguments();

  Object mock = invocation.getMock();

  return "called with arguments: " + args;

  }

  });

  //the following prints "called with arguments: foo"

  System.out.println(mock.someMethod("foo"));

  Mock函数操作

  可以通过doThrow(), doAnswer(), doNothing(), doReturn() and doCallRealMethod() 来自定义函数操作。

  暗中调用真实对象

  List list = new LinkedList();

  List spy = spy(list);

  //optionally, you can stub out some methods:

  when(spy.size()).thenReturn(100);

  //using the spy calls *real* methods

  spy.add("one");

  spy.add("two");

  //prints "one" - the first element of a list

  System.out.println(spy.get(0));

  //size() method was stubbed - 100 is printed

  System.out.println(spy.size());

  //optionally, you can verify

  verify(spy).add("one");

  verify(spy).add("two");

  改变默认返回值

  Foo mock = mock(Foo.class, Mockito.RETURNS_SMART_NULLS);

  Foo mockTwo = mock(Foo.class, new YourOwnAnswer());

  捕获函数的参数值

  ArgumentCaptor argument = ArgumentCaptor.forClass(Person.class);

  verify(mock).doSomething(argument.capture());

  assertEquals("John", argument.getValue().getName());

  部分Mock

  //you can create partial mock with spy() method:

  List list = spy(new LinkedList());

  //you can enable partial mock capabilities selectively on mocks:

  Foo mock = mock(Foo.class);

  //Be sure the real implementation is 'safe'.

  //If real implementation throws exceptions or depends on specific state of the object then you're in trouble.

  when(mock.someMethod()).thenCallRealMethod();

  重置Mock

  List mock = mock(List.class);

  when(mock.size()).thenReturn(10);

  mock.add(1);

  reset(mock);

  //at this point the mock forgot any interactions & stubbing

  序列化

  List list = new ArrayList();

  List spy = mock(ArrayList.class, withSettings()

  .spiedInstance(list)

  .defaultAnswer(CALLS_REAL_METHODS)

  .serializable());

  检查超时

  //passes when someMethod() is called within given time span

  verify(mock, timeout(100)).someMethod();

  //above is an alias to:

  verify(mock, timeout(100).times(1)).someMethod();

  //passes when som`eMethod() is called *exactly* 2 times within given time span

  verify(mock, timeout(100).times(2)).someMethod();

  //passes when someMethod() is called *at least* 2 times within given time span

  verify(mock, timeout(100).atLeast(2)).someMethod();

  //verifies someMethod() within given time span using given verification mode

  //useful only if you have your own custom verification modes.

  verify(mock, new Timeout(100, yourOwnVerificationMode)).someMethod();

  Mock详情

  Mockito.mockingDetails(someObject).isMock();

  Mockito.mockingDetails(someObject).isSpy();

  文/流水不腐小夏(简书作者)

  原文链接:http://www.jianshu.com/p/77db26b4fb54

  著作权归作者所有,转载请联系作者获得授权,并标注“简书作者”。

 

 

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