Java Mock 对象，没有依赖注入(inject)

Question

我对 JUnit 测试套件中的模拟对象很感兴趣，但是我只遇到过使用依赖注入(inject)来注入(inject)模拟对象的模拟框架。但是，我希望能够模拟类/函数而不必注入(inject)该模拟对象，就像 python 中的 @patch() 一样。

简单的例子:

//dependency injection
public String bar(Foo foo) {
    return foo.foo(); //just pass in mock Foo object
}
//.... onto test code
Foo mockedFoo = <Mocked Foo object>;
String response = bar(mockedFoo);
assertEqual(response, <mockedFoo return value>);


//case I am looking for
public String bar() {
    Foo foo = new Foo(); //how to create mock object here?
    return foo.foo(); //or simply how to mock a single function?
}
//... onto test code
<force the Foo class or foo method to be mocked from here without touching bar() source code>
String response = bar();
assertEqual(response, <mocked response>);

Answer 1

您可以使用 Powermock 检测被测类，以便在调用 new 时返回模拟。

Powermock mock constructor tutorial

你的代码看起来像这样:

RunWith(PowerMockRunner.class)
@PrepareForTest( Bar.class )
public class BarTest {


@Test
public void test(){
   Foo mockedFoo = createMock(Foo.class);
   //set up mockedFoo here
   ...

   //This will make a call  to new Foo() inside Bar.class
   //return your mock instead of a real new one
   expectNew(Foo.class).andReturn(mockedFoo);

   ...
   replay(mockedFoo, File.class);

   Bar bar = new Bar();
   String response = bar.bar();

   assertEqual(response, <mocked response>);

   verify(mockedFoo, File.class);


}

}