为 Factory 类创建的对象注入 Mocks

Inject Mocks for objects created by Factory classes(为 Factory 类创建的对象注入 Mocks)

问题描述

我有以下课程:

public class MyClass {        
    private Apple apple;

    public void myMethod() {
       apple = AppleFactory.createInstance(someStringVariable);
       ....
       ....
       ....
    }
}

还有测试类:

@RunWith(MockitoJUnitRunner.class)
public class MyClassTest {

        @InjectMocks 
        MyClass myClass;

        @Test
        public void myMethod(){
         ...
         ...
         ...
        }
    }

如何在 MyClass 中注入 Apple 实例作为模拟?

How could I inject an Apple instance as a mock in MyClass?

推荐答案

你有 3 种可能解决这个问题:

You have 3 possibilities to solve this:

抽象工厂:不要使用静态方法，而是使用具体工厂类:

Abstract factory: Instead of using a static method, use a concrete factory class:

public abstract class AppleFactory {
    public Apple createInstance(final String str);
}

public class AppleFactoryImpl implements AppleFactory {
    public Apple createInstance(final String str) { // Implementation }
}

在您的测试类中，模拟工厂:

In your test class, mock the factory:

@RunWith(MockitoJUnitRunner.class)
public class MyClassTest {

    @Mock
    private AppleFactory appleFactoryMock;

    @Mock
    private Apple appleMock;

    @InjectMocks 
    MyClass myClass;

    @Before
    public void setup() {
        when(appleFactoryMock.createInstance(Matchers.anyString()).thenReturn(appleMock);
    }

    @Test
    public void myMethod(){
     ...
     ...
     ...
    }
}

PowerMock:使用 PowerMock 创建静态方法的模拟.查看我对相关问题的回答了解它是如何完成的.

PowerMock: Use PowerMock to create a mock of a static method. Look at my answer to a relevant question to see how it's done.

可测试类:将 Apple 创建包装在 protected 方法中，并创建一个覆盖它的测试类:

Testable class: Make the Apple creation wrapped in a protected method and create a test class that overrides it:

public class MyClass {
   private Apple apple;

   public void myMethod() {
       apple = createApple();
       ....
       ....
       ....
   }

   protected Apple createApple() {
       return AppleFactory.createInstance(someStringVariable);
   }
}


@RunWith(MockitoJUnitRunner.class)
public class MyClassTest {

    @Mock
    private Apple appleMock;

    @InjectMocks 
    MyClass myClass;

    @Test
    public void myMethod(){
     ...
     ...
     ...
    }

    private class TestableMyClass extends MyClass {
       @Override
       public void createApple() {
          return appleMock;
       }
    }
}

当然，在你的测试类中你应该测试 TestableMyClass 而不是 MyClass.

Of course, in your test class you should test TestableMyClass and not MyClass.

我会告诉你我对每种方法的看法:

I'll tell you my opinion on each of the methods:

1. 抽象工厂方法是最好的一个 - 这是一个隐藏实现细节的清晰设计

1. The abstract factory method is the best one - This is a clear design that hides the implementation details

可测试类 - 是第二个需要最少更改的选项

The testable class - Is the second option which requires minimum changes

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