使用PowerMockito模拟getClass方法 [英] Mocking getClass method with PowerMockito

问题描述

我想避免为类嘲笑getClass()方法，但似乎找不到任何解决方法.我正在尝试测试一个将对象类类型存储在HashMap中的类，以供以后使用的特定方法.一个简单的例子是:

I'd like to avoid mocking the getClass() method for a class but cannot seem to find any way around it. I'm trying to test a class that stores objects class types in a HashMap to a particular method to be used later. A brief example of this is:

public class ClassToTest {
    /** Map that will be populated with objects during constructor */
    private Map<Class<?>, Method> map = new HashMap<Class<?>, Method>();

    ClassToTest() {
        /* Loop through methods in ClassToTest and if they return a boolean and 
           take in an InterfaceA parameter then add them to map */
    }

    public void testMethod(InterfaceA obj) {
        final Method method = map.get(obj.getClass());
        boolean ok;
        if (method != null) {
             ok = (Boolean) method.invoke(this, obj);
        }
        if (ok) {
            obj.run();
        }
    }

    public boolean isSafeClassA(final ClassA obj) {
        // Work out if safe to run and then return true/false
    }

    public boolean isSafeClassB(final ClassB obj) {
       // Work out if safe to run and then return true/fals 
    }

}

public interface InterfaceA {
   void run()
}

public class ClassA implements InterfaceA {
   public void run() {
      // implements method here
   }
}

public class ClassB implements InterfaceA {
    public void run() {
       // implements method here
    }
}

然后我有一个看起来像这样的JUnit测试:

I then have a JUnit test that looks a little like this:

@RunWith(PowerMockRunner.class)
@PrepareForTest({ClassA.class})
public class ClassToTestTest {
    private final ClassToTest tester = new ClassToTest();

    @Test
    public void test() {
        MockGateway.MOCK_GET_CLASS_METHOD = true;
        final ClassA classA = spy(new ClassA());
        doReturn(ClassA.class).when(classA).getClass();
        MockGateway.MOCK_GET_CLASS_METHOD = false;

        tester.testMethod(classA);
        verify(classA).run();
    }
}

我的问题是尽管在test()方法中是classA.getClass();将返回ClassA，一旦进入测试人员的testMethod()方法，它仍将返回ClassA $ EnhancerByMockitoWithCGLIB $ ...类，因此我有用的对象将始终为null.

My problem is although inside the test() method classA.getClass(); will return ClassA, once inside tester's testMethod() method it still returns the ClassA$EnhancerByMockitoWithCGLIB$... class and so my object useful will always be null.

我有什么办法可以解决该类的问题，或者我需要做些什么来解决这个问题?

Is there any way I can get around mocking the class or what do I need to do to fix this?

谢谢.

推荐答案

哇，要使此代码可测试真是令人头疼.主要问题是您不能在调用map.get(obj.getClass())的过程中将模拟对象用作key对象，并且正在尝试invoke()可能模拟对象进行测试.我必须重构您的测试类，以便我们可以模拟功能/行为并能够验证其行为.

Wow, what a headache to get this code testable. The main issues are that you can't use mock objects as key objects into your calls to map.get(obj.getClass()), and you're trying to invoke() potentially mock objects for your testing. I had to refactor your class under test so that we can mock out the functionality/behaviour and be able to verify its behaviour.

这是您的新实现，将用成员变量解耦各种功能故障并由测试类注入的成员变量进行测试

So this is your new implementation to be tested with member variables decoupling the various pieces of functionailty and injected by the test class

public class ClassToTest {

    MethodStore methodStore;
    MethodInvoker methodInvoker;
    ClassToInvoke classToInvoke;
    ObjectRunner objectRunner;  

    public void testMethod(InterfaceA obj) throws Exception {

        Method method = methodStore.getMethod(obj);

        boolean ok = false;

        if (method != null) {
            ok = methodInvoker.invoke(method, classToInvoke, obj);
        }

        if (ok) {
            objectRunner.run(obj);
        }   
    }

    public void setMethodStore(MethodStore methodStore) {
        this.methodStore = methodStore;
    }

    public void setMethodInvoker(MethodInvoker methodInvoker) {
        this.methodInvoker = methodInvoker;
    }

    public void setObjectRunner(ObjectRunner objectRunner) {
        this.objectRunner = objectRunner;
    }

    public void setClassToInvoke(ClassToInvoke classToInvoke) {
        this.classToInvoke = classToInvoke;
    }
}

这是您的测试类，不再需要PowerMock，因为它无法模拟方法类.它只返回NullPointerException.

This is your test class that no longer requires PowerMock, because it can't mock the Method class. It just returns a NullPointerException.

public class MyTest {

    @Test
    public void test() throws Exception {

        ClassToTest classToTest = new ClassToTest();

        ClassA inputA = new ClassA();

        // trying to use powermock here just returns a NullPointerException
//      final Method mockMethod = PowerMockito.mock(Method.class);
        Method mockMethod = (new ClassToInvoke()).getClass().getMethod("someMethod");   // a real Method instance

        // regular mockito for mocking behaviour    
        ClassToInvoke mockClassToInvoke = mock(ClassToInvoke.class);
        classToTest.setClassToInvoke(mockClassToInvoke);

        MethodStore mockMethodStore = mock(MethodStore.class);
        classToTest.setMethodStore(mockMethodStore);

        when(mockMethodStore.getMethod(inputA)).thenReturn(mockMethod);

        MethodInvoker mockMethodInvoker = mock(MethodInvoker.class);
        classToTest.setMethodInvoker(mockMethodInvoker);

        when(mockMethodInvoker.invoke(mockMethod,mockClassToInvoke, inputA)).thenReturn(Boolean.TRUE);

        ObjectRunner mockObjectRunner = mock(ObjectRunner.class);
        classToTest.setObjectRunner(mockObjectRunner);

        // execute test method      
        classToTest.testMethod(inputA);

        verify(mockObjectRunner).run(inputA);   
    }
}

您需要的其他类如下

public class ClassToInvoke {
    public void someMethod() {};
}

public class ClassA implements InterfaceA {

    @Override
    public void run() {
        // do something
    }
}

public class ClassToInvoke {
    public void someMethod() {};
}

public class MethodInvoker {

    public Boolean invoke(Method method, Object obj, InterfaceA a) throws Exception {
         return (Boolean) method.invoke(obj, a);
    }
}

public class MethodStore {

    Map<Class<?>, Method> map = new HashMap<Class<?>, Method>();

    public Method getMethod(InterfaceA obj) {
        return map.get(obj);
    }
}

将所有这些内容放入您的IDE中，它会带有绿色的条...呜呼！

Put all this into your IDE and it will pass with a Green bar...woohoo!

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