Spring：如何测试被其他方法调用的方法的参数及对象创建？

针对调用emitObject()后需要验证的三项内容，这里用Mockito框架给出具体测试实现方案：

验证someMethod()是否被调用 #

通过Spy或Mock目标类，调用emitObject()后用verify方法确认someMethod是否被触发：

@Test
void testEmitObjectTriggersSomeMethod() {
    // 假设当前类为Emitter，创建Spy对象（若someMethod是当前类方法）
    Emitter emitter = Mockito.spy(new Emitter());
    CustomObject obj1 = new CustomObject();
    CustomObject obj2 = new CustomObject();

    emitter.emitObject(obj1, obj2);

    // 验证someMethod被调用至少一次，参数为任意anotherObject实例
    Mockito.verify(emitter).someMethod(Mockito.any(anotherObject.class));
}

验证anotherObject()是否成功创建 #

结合ArgumentCaptor捕获传入someMethod的参数，只要捕获到的实例不为null，即可证明anotherObject已成功创建：

@Test
void testEmitObjectCreatesAnotherObject() {
    Emitter emitter = Mockito.spy(new Emitter());
    CustomObject obj1 = new CustomObject();
    CustomObject obj2 = new CustomObject();

    emitter.emitObject(obj1, obj2);

    ArgumentCaptor<anotherObject> captor = ArgumentCaptor.forClass(anotherObject.class);
    Mockito.verify(emitter).someMethod(captor.capture());

    // 断言捕获到的实例不为null
    assertNotNull(captor.getValue());
}

验证anotherObject构造方法的参数值 #

用ArgumentCaptor捕获实例后，通过getter方法验证构造参数是否与预期一致：

@Test
void testAnotherObjectHasCorrectConstructorParams() {
    Emitter emitter = Mockito.spy(new Emitter());
    // 构造测试用的CustomObject实例并设置属性
    CustomObject obj1 = new CustomObject();
    obj1.setSomeProp1("expectedProp1");
    obj1.setSomeProp2("expectedProp2");
    CustomObject obj2 = new CustomObject();
    obj2.setSomeProp1("expectedProp3");
    obj2.setSomeProp2("expectedProp4");

    emitter.emitObject(obj1, obj2);

    ArgumentCaptor<anotherObject> captor = ArgumentCaptor.forClass(anotherObject.class);
    Mockito.verify(emitter).someMethod(captor.capture());

    anotherObject createdObj = captor.getValue();
    // 验证每个构造参数对应的属性值
    assertEquals("expectedProp1", createdObj.getSomeProp1());
    assertEquals("expectedProp2", createdObj.getSomeProp2());
    assertEquals("expectedProp3", createdObj.getSomeProp3());
    assertEquals("expectedProp4", createdObj.getSomeProp4());
}

如果anotherObject未提供属性getter，也可以在verify时直接用Lambda匹配参数：

Mockito.verify(emitter).someMethod(Mockito.argThat(obj -> 
    obj.getSomeProp1().equals("expectedProp1") &&
    obj.getSomeProp2().equals("expectedProp2") &&
    obj.getSomeProp3().equals("expectedProp3") &&
    obj.getSomeProp4().equals("expectedProp4")
));

内容的提问来源于stack exchange，提问作者WhatHappenedHere