blocks|key|1153838|text|模拟对象是替代真实对象的对象。在面向对象编程中，模拟对象是以受控方式模仿真实对象行为的模拟对象。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1153839|计算机程序员通常创建模拟对象来测试某些其他对象的行为，这与汽车设计者使用碰撞测试假人来模拟人在车辆碰撞中的动态行为非常相似。|1153840|http://en.wikipedia.org/wiki/Mock_object|offset|length|1153841|模拟对象允许您设置测试场景，而无需使用大型、笨重的资源，如数据库。您可以在单元测试中使用模拟对象模拟数据库，而不是调用数据库进行测试。这使您摆脱了必须设置和拆卸实际数据库的负担，仅仅是为了在类中测试单个方法。|1153842|单词"Mock“有时错误地与”Stub“互换使用。这两个词之间的区别本质上是described+here.，mock是一个存根对象，它还包括对被测对象/方法的正确行为的期望(即“断言”)。|1153843|例如：|1153844|class+OrderInteractionTester...
++public+void+testOrderSendsMailIfUnfilled()+{
++++Order+order+=+new+Order(TALISKER,+51);
++++Mock+warehouse+=+mock(Warehouse.class);
++++Mock+mailer+=+mock(MailService.class);
++++order.setMailer((MailService)+mailer.proxy());

++++mailer.expects(once()).method("send");
++++warehouse.expects(once()).method("hasInventory")
++++++.withAnyArguments()
++++++.will(returnValue(false));

++++order.fill((Warehouse)+warehouse.proxy());
++}
}|code-block|syntax|javascript|1153845|注意，使用预期的结果对warehouse和mailer模拟对象进行了编程。|style|CODE|1153846|entityMap|0|LINK|mutability|MUTABLE|url|1|http://martinfowler.com/articles/mocksArentStubs.html#TheDifferenceBetweenMocksAndStubs^0|0|0|0|14|0|0|0|12|F|1|0|0|0|B|9|L|6|0^^$0|@$1|2|3|4|5|6|7|15|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|16|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|17|8|@]|9|@$F|18|G|19|1|1A]]|A|$]]|$1|H|3|I|5|6|7|1B|8|@]|9|@]|A|$]]|$1|J|3|K|5|6|7|1C|8|@]|9|@$F|1D|G|1E|1|1F]]|A|$]]|$1|L|3|M|5|6|7|1G|8|@]|9|@]|A|$]]|$1|N|3|O|5|P|7|1H|8|@]|9|@]|A|$Q|R]]|$1|S|3|T|5|6|7|1I|8|@$F|1J|G|1K|U|V]|$F|1L|G|1M|U|V]]|9|@]|A|$]]|$1|W|3|-4|5|6|7|1N|8|@]|9|@]|A|$]]]|X|$Y|$5|Z|10|11|A|$12|E]]|13|$5|Z|10|11|A|$12|14]]]]

A Mock Object is an object that substitutes for a real object. In object-oriented programming, mock objects are simulated objects that mimic the behavior of real objects in controlled ways.

A computer programmer typically creates a mock object to test the behavior of some other object, in much the same way that a car designer uses a crash test dummy to simulate the dynamic behavior of a human in vehicle impacts.

<a href="http://en.wikipedia.org/wiki/Mock_object" rel="noreferrer">http://en.wikipedia.org/wiki/Mock_object</a>

Mock objects allow you to set up test scenarios without bringing to bear large, unwieldy resources such as databases. Instead of calling a database for testing, you can simulate your database using a mock object in your unit tests. This frees you from the burden of having to set up and tear down a real database, just to test a single method in your class.

The word "Mock" is sometimes erroneously used interchangeably with "Stub." The differences between the two words are <a href="http://martinfowler.com/articles/mocksArentStubs.html#TheDifferenceBetweenMocksAndStubs" rel="noreferrer">described here.</a> Essentially, a mock is a stub object that also includes the expectations (i.e. "assertions") for proper behavior of the object/method under test. 

For example:

<pre><code>class OrderInteractionTester...
 public void testOrderSendsMailIfUnfilled() {
 Order order = new Order(TALISKER, 51);
 Mock warehouse = mock(Warehouse.class);
 Mock mailer = mock(MailService.class);
 order.setMailer((MailService) mailer.proxy());

 mailer.expects(once()).method("send");
 warehouse.expects(once()).method("hasInventory")
 .withAnyArguments()
 .will(returnValue(false));

 order.fill((Warehouse) warehouse.proxy());
 }
}
</code></pre>

Notice that the <code>warehouse</code> and <code>mailer</code> mock objects are programmed with the expected results.

blocks|key|1153888|text|我强烈推荐一个great+article+by+Martin+Fowler，解释模拟到底是什么，以及它们与存根有何不同。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1153889|entityMap|0|LINK|mutability|MUTABLE|url|http://martinfowler.com/articles/mocksArentStubs.html^0|7|U|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@$A|M|B|N|1|O]]|C|$]]|$1|D|3|-4|5|6|7|P|8|@]|9|@]|C|$]]]|E|$F|$5|G|H|I|C|$J|K]]]]

I highly recommend a <a href="http://martinfowler.com/articles/mocksArentStubs.html" rel="noreferrer">great article by Martin Fowler</a> explaining what exactly are mocks and how they differ from stubs.

blocks|key|1153948|text|模拟对象是一种Test+Double。您正在使用mockobjects来测试和验证被测类与其他类的协议/交互。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1153949|通常，你会“编程”或“记录”期望:你期望你的类对底层对象进行的方法调用。|1153950|比方说，我们正在测试一个服务方法来更新Widget中的字段。在您的体系结构中，有一个处理数据库的WidgetDAO。与数据库的对话很慢，设置和事后清理也很复杂，所以我们将模拟WidgetDao。|1153951|让我们考虑一下服务必须做什么:它应该从数据库中获取一个Widget，使用它做一些事情，然后再次保存它。|1153952|因此，在带有伪模拟库的伪语言中，我们会有如下内容：|1153953|Widget+sampleWidget+=+new+Widget();
WidgetDao+mock+=+createMock(WidgetDao.class);
WidgetService+svc+=+new+WidgetService(mock);

//+record+expected+calls+on+the+dao
expect(mock.getById(id)).andReturn(sampleWidget);+++
expect(mock.save(sampleWidget);

//+turn+the+dao+in+replay+mode
replay(mock);

svc.updateWidgetPrice(id,newPrice);

verify(mock);++++//+verify+the+expected+calls+were+made
assertEquals(newPrice,sampleWidget.getPrice());|code-block|syntax|javascript|1153954|通过这种方式，我们可以很容易地测试驱动依赖于其他类的类的开发。|1153955|entityMap|0|LINK|mutability|MUTABLE|url|http://xunitpatterns.com/Test%2520Double.html^0|7|B|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|10|8|@]|9|@$A|11|B|12|1|13]]|C|$]]|$1|D|3|E|5|6|7|14|8|@]|9|@]|C|$]]|$1|F|3|G|5|6|7|15|8|@]|9|@]|C|$]]|$1|H|3|I|5|6|7|16|8|@]|9|@]|C|$]]|$1|J|3|K|5|6|7|17|8|@]|9|@]|C|$]]|$1|L|3|M|5|N|7|18|8|@]|9|@]|C|$O|P]]|$1|Q|3|R|5|6|7|19|8|@]|9|@]|C|$]]|$1|S|3|-4|5|6|7|1A|8|@]|9|@]|C|$]]]|T|$U|$5|V|W|X|C|$Y|Z]]]]

A Mock object is one kind of a <a href="http://xunitpatterns.com/Test%20Double.html" rel="noreferrer">Test Double</a>. You are using mockobjects to test and verify the protocol/interaction of the class under test with other classes.

Typically you will kind of 'program' or 'record' expectations : method calls you expect your class to do to an underlying object. 

Let's say for example we are testing a service method to update a field in a Widget. And that in your architecture there is a WidgetDAO which deals with the database. Talking with the database is slow and setting it up and cleaning afterwards is complicated, so we will mock out the WidgetDao.

let's think what the service must do : it should get a Widget from the database, do something with it and save it again.

So in pseudo-language with a pseudo-mock library we would have something like :

<pre><code>Widget sampleWidget = new Widget();
WidgetDao mock = createMock(WidgetDao.class);
WidgetService svc = new WidgetService(mock);

// record expected calls on the dao
expect(mock.getById(id)).andReturn(sampleWidget); 
expect(mock.save(sampleWidget);

// turn the dao in replay mode
replay(mock);

svc.updateWidgetPrice(id,newPrice);

verify(mock); // verify the expected calls were made
assertEquals(newPrice,sampleWidget.getPrice());
</code></pre>

In this way we can easily test drive development of classes which depend on other classes.

blocks|key|1153980|text|作为另一个答案，通过链接到"Mocks+Aren't+Stubs"，模拟是“测试替身”的一种形式，用来代替真实的对象。它们与其他形式的测试替身(例如存根对象)的不同之处在于，其他测试替身提供状态验证(以及可选的模拟)，而模拟提供行为验证(以及可选的模拟)。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1153981|使用存根，您可以按任何顺序(甚至重复)调用存根上的几个方法，并确定存根是否捕获了您想要的值或状态。相比之下，模拟对象期望以特定的顺序甚至特定的次数调用非常特定的函数。使用模拟对象的测试将被认为是“失败的”，因为这些方法是以不同的顺序或计数调用的-即使模拟对象在测试结束时具有正确的状态！|1153982|在这种情况下，模拟对象通常被认为与SUT代码的耦合比存根对象更紧密。这可能是好事，也可能是坏事，这取决于您试图验证的内容。|1153983|entityMap|0|LINK|mutability|MUTABLE|url|http://martinfowler.com/articles/mocksArentStubs.html#TheDifferenceBetweenMocksAndStubs^0|E|I|0|0|0|0^^$0|@$1|2|3|4|5|6|7|P|8|@]|9|@$A|Q|B|R|1|S]]|C|$]]|$1|D|3|E|5|6|7|T|8|@]|9|@]|C|$]]|$1|F|3|G|5|6|7|U|8|@]|9|@]|C|$]]|$1|H|3|-4|5|6|7|V|8|@]|9|@]|C|$]]]|I|$J|$5|K|L|M|C|$N|O]]]]

As another answer suggested via a link to "<a href="http://martinfowler.com/articles/mocksArentStubs.html#TheDifferenceBetweenMocksAndStubs" rel="nofollow noreferrer">Mocks Aren't Stubs</a>", mocks are a form of "test double" to use in lieu of a real object. What makes them different from other forms of test doubles, such as stub objects, is that other test doubles offer state verification (and optionally simulation) whereas mocks offer behavior verification (and optionally simulation).

With a stub, you might call several methods on the stub in any order (or even repitiously) and determine success if the stub has captured a value or state you intended. In contrast, a mock object expects very specific functions to be called, in a specific order, and even a specific number of times. The test with a mock object will be considered "failed" simply because the methods were invoked in a different sequence or count - even if the mock object had the correct state when the test concluded!

In this way, mock objects are often considered more tightly coupled to the SUT code than stub objects. That can be a good or bad thing, depending on what you are trying to verify.

blocks|key|1153993|text|php和phpunit在phpunit文档中有很好的解释。查看此处phpunit+documentation|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1153994|简单地说，模拟对象只是原始对象的虚拟对象，并返回其返回值，此返回值可以在测试类中使用|1153995|entityMap|0|LINK|mutability|MUTABLE|url|https://phpunit.de/manual/current/en/test-doubles.html#test-doubles.mock-objects^0|X|L|0|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@]|9|@$A|O|B|P|1|Q]]|C|$]]|$1|D|3|E|5|6|7|R|8|@]|9|@]|C|$]]|$1|F|3|-4|5|6|7|S|8|@]|9|@]|C|$]]]|G|$H|$5|I|J|K|C|$L|M]]]]

For php and phpunit is well explained in phpunit documentaion. see here
<a href="https://phpunit.de/manual/current/en/test-doubles.html#test-doubles.mock-objects" rel="nofollow">phpunit documentation</a>

In simple word mocking object is just dummy object of your original one and is return its return value, this return value can be used in the test class

blocks|key|939702|text|这是单元测试的主要观点之一。是的，您正在尝试测试您的单个代码单元，并且您的测试结果不应该与其他bean或对象行为相关。因此，您应该通过使用mock对象和一些简化的相应响应来模拟它们。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|939703|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

It's one of the main perspectives of unit tests. yes, you're trying to test your single unit of code and your test results should not be relevant to other beans or objects behavior. so you should mock them by using Mock objects with some simplified corresponding response.

I am new to unit testing, and I continously hear the words 'mock objects' thrown around a lot. In layman's terms, can someone explain what mock objects are, and what they are typically used for when writing unit tests?

What is the purpose of mock objects?

单元测试

数据库

我是单元测试的新手，我经常听到“模拟对象”的说法。用外行的话来说，有人能解释一下什么是模拟对象，以及它们在编写单元测试时通常用于什么？

问模拟对象的用途是什么？
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