我不能理解junit mockito测试中willThrow、doThrow的逻辑

when(mockObject.someMethod()).willThrow(ExceptionClass.class);

@Test(expected = SomeException.class)
public void testSomeMethod() throws SomeException {
    MockObject mockObject = mock(MockObject.class);
    when(mockObject.someMethod()).willThrow(SomeException.class);
    // ...
    // 执行测试代码，调用someMethod方法
    // ...
}

doThrow(ExceptionClass.class).when(mockObject).someMethod();

@Test(expected = SomeException.class)
public void testSomeMethod() throws SomeException {
    MockObject mockObject = mock(MockObject.class);
    doThrow(SomeException.class).when(mockObject).someMethod();
    // ...
    // 执行测试代码，调用someMethod方法
    // ...
}