Mockito定义模拟类型转换时的行为

Question

public class MyClass {
  public String myMethod(ObjectString arg) {
    ans = (String) arg;
    return ans;
  } 
}

public class MyClassTest {
  @Test
  public void myMethod_should_convert_to_string() {
    MyClass testMyClass = new MyClass();
    ObjectString mockObjectString = Mockito.mock(ObjectString.class);
    String expected = "expected string returned";
    Mockito.when(mockObjectString.IS_CAST_TO_STRING).thenReturn(expected);
    String actual = testMyClass.myMethod(mockObjectString);
    Assert.assertEquals(expected, actual);
  }
}

Answer 1

ObjectString的实例永远不能强制转换为String。String不从任何名为ObjectString的类继承，也不实现任何名为ObjectString的接口。转换为String将始终引发ClassCastException，除非Arg为Null。

另一方面，如果测试中的类如下所示：

public class MyClass {
    public String myMethod(final Object arg) {
        final String ans = (String) arg;
        return ans;
    }
}

然后,您可以在没有Mockito的情况下实现您想要的目标：

@Test
public void myMethod_should_convert_to_string() {
    MyClass testMyClass = new MyClass();
    String expected = "expected string returned";
    String actual = testMyClass.myMethod(expected);
    assertEquals(expected, actual);
}