Question

我有这样的结构：

public class CacheWrapper {
    private Map<Object, Object> innerMap;

    public CacheWrapper() {
        //initialize the innerMap with an instance for an in-memory cache
        //that works on external server
        //current implementation is not relevant for the problem
        innerMap = ...;
    }

    public void putInSharedMemory(Object key, Object value) {
        innerMap.put(key, value);
    }

    public Object getFromSharedMemory(Object key) {
        return innerMap.get(key);
    }
}

我的客户端类（你可以说它看起来像这样）：

public class SomeClient {
    //Logger here, for exception handling
    Logger log = ...;
    private CacheWrapper cacheWrapper;
    //getter and setter for cacheWrapper...

    public Entity getEntity(String param) {
        Entity someEntity = null;
        try {
            try {
                entity = cacheWrapper.getFromSharedMemory(param);
            } catch (Exception e) {
                //probably connection failure occurred here
                log.warn("There was a problem when getting from in-memory " + param + " key.", e);
            }
            if (entity == null) {
                entity = ...; //retrieve it from database
                //store in in-memory cache
                try {
                    cacheWrapper.put(param, entity);
                } catch (Exception e) {
                    //probably connection failure occurred here
                    log.warn("There was a problem when putting in in-memory " + param + " key.", e);
                }
            }
        } catch (Exception e) {
            logger.error(".......", e);
        }
        return entity;
    }
}

我正在为SomeClient#getEntity方法创建单元测试，并且必须涵盖所有方案。例如，我需要介绍cacheWrapper引发异常的情况。我接下来的方法是为CacheWrapper类创建一个模拟，让CacheWrapper类上的方法抛出RuntimeException，在{{1}的实例中设置这个模拟并测试SomeClient。问题在于尝试模拟Someclient#getEntity方法，因为putInSharedMemory。我已经尝试了很多方法来做到这一点，但没有一个工作。 该项目依赖于PowerMock和EasyMock 。

以下是我的尝试：

使用void。这引发了编译错误。
尝试使用存根EasyMock.<Void>expect。没有用，因为这个错误消息引发了异常：

java.lang.AssertionError：意外的方法调用putInSharedMemory（＆＃34; foo＆＃34;，com.company.domain.Entity@609fc98）
为项目添加了Mockito依赖项以利用CacheWrapper#putInSharedMemory类的功能。但这引发了一个例外，因为它没有与EasyMock集成。这是一个例外：

java.lang.ClassCastException：org.powermock.api.easymock.internal.invocationcontrol.EasyMockMethodInvocationControl无法强制转换为org.powermock.api.mockito.internal.invocationcontrol.MockitoMethodInvocationControl

以下是此单元测试样本的代码：

PowerMockito

我无法更改@Test public void getEntityWithCacheWrapperException() { CacheWrapper cacheWrapper = mockThrowsException(); SomeClient someClient = new SomeClient(); someClient.setCacheWrapper(cacheWrapper); Entity entity = someClient.getEntity(); //here.....................^ //cacheWrapper.putInSharedMemory should throw an exception //start asserting here... } //... public CacheWrapper mockThrowsException() { CacheWrapper cacheWrapper = PowerMock.createMock(CacheWrapper.class); //mocking getFromSharedMemory method //this works like a charm EasyMock.expect(cacheWrapper.getFromSharedMemory(EasyMock.anyObject())) .andThrow(new RuntimeException("This is an intentional Exception")).anyTimes(); //mocking putInSharedMemory method //the pieces of code here were not executed at the same time //instead they were commented and choose one approach after another //attempt 1: compiler exception: <Void> is not applicable for <void> EasyMock.<Void>expect(cacheWrapper.putInSharedMemory(EasyMock.anyObject(), EasyMock.anyObject())) .andThrow(new RuntimeException("This is an intentional Exception")).anyTimes(); //attempt 2: stubbing the method //exception when executing the test: //Unexpected method call putInSharedMemory("foo", com.company.domain.Entity@609fc98) Method method = PowerMock.method(CacheWrapper.class, "putInSharedMemory", Object.class, Object.class); PowerMock.stub(method).toThrow(new RuntimeException("Exception on purpose.")); //attempt 3: added dependency to Mockito integrated to PowerMock //bad idea: the mock created by PowerMock.createMock() belongs to EasyMock, not to Mockito //so it breaks when performing the when method //exception: //java.lang.ClassCastException: org.powermock.api.easymock.internal.invocationcontrol.EasyMockMethodInvocationControl //cannot be cast to org.powermock.api.mockito.internal.invocationcontrol.MockitoMethodInvocationControl //at org.powermock.api.mockito.internal.expectation.PowerMockitoStubberImpl.when(PowerMockitoStubberImpl.java:54) PowerMockito.doThrow(new RuntimeException("Exception on purpose.")) .when(cacheWrapper).putInSharedMemory(EasyMock.anyObject(), EasyMock.anyObject()); PowerMock.replay(cacheWrapper); return cacheWrapper; }的实现，因为它来自第三方库。另外，我无法使用CacheWrapper，因为我正在EasyMock#getLastCall上执行测试。

我怎样才能克服这个？

Answer 1

由于您的课程都不是最终的，您可以使用“纯粹的模拟”，而无需使用PowerMockito：

final CacheWrapper wrapper = Mockito.spy(new CacheWrapper());

Mockito.doThrow(something)
    .when(wrapper).putInSharedMemory(Matchers.any(), Matchers.any());

请注意，存根的“方法参数”实际上是参数匹配器;您可以设置特定值（如果没有被特定方法“包围”，它将调用.equals()）。因此，您可以针对不同的参数不同地指导存根的行为。

此外，Mockito不需要任何.replay()，这非常好！

最后，请注意您也可以doCallRealMethod()。在那之后，这取决于你的场景......

（注意：maven上可用的最后一个版本是1.10.17 FWIW）

Answer 2

您使用的是EasyMock还是Mockito？两者都是不同的框架。

PowerMockito是可以与这两个框架一起使用的超集（或更多补充）。 PowerMockito允许你做Mockito或EasyMock不做的事情。

尝试使用此方法来存储void方法以抛出异常：

<强> EasyMock的：

// First make the actual call to the void method.
cacheWrapper.putInSharedMemory("key", "value");
EasyMock.expectLastCall().andThrow(new RuntimeException());

检查：

Mockito：

 // Create a CacheWrapper spy and stub its method to throw an exception.
 // Syntax for stubbing a spy's method is different from stubbing a mock's method (check Mockito's docs).
 CacheWrapper spyCw = spy(new CacheWrapper()); 
 Mockito.doThrow(new RuntimeException())
     .when(spyCw)
     .putInSharedMemory(Matchers.any(), Matchers.any());

 SomeClient sc = new SomeClient();
 sc.setCacheWrapper(spyCw);

 // This will call spyCw#putInSharedMemory that will throw an exception.
 sc.getEntity("key");

Answer 3

使用expectLastCall，例如：

    cacheWrapper.putInSharedMemory(EasyMock.anyObject(), EasyMock.anyObject())
    EasyMock.expectLastCall().andThrow(new RuntimeException("This is an intentional Exception")).anyTimes();

如何模拟void方法抛出异常？

3 个答案: