Mocking constructor - is it possible?

[Hr Borisov]

I have the following question: When we have a local object for a method and we
invoke a constructor for that object, can we catch the invocation to the
constructor and mock the creation of the object?
I know that I can make a mock of the invocation of some method in a class not
depending on the reference but it would not help me. For example if I want to
mock isEmpty() method of some collection object I could not because I can't
calculate the consecutive number of the invocation that is important to me.
Thanks in advance!

Example:

Class A {
  void someMethod() {
    B ref = new B();

    if (ref.doSomething() == 10) {
      // I want to get here by mocking ref
    }
  }
}

Class B {
  int doSomething() {
   ...
  }
}



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[Steve Freeman-2]

We can't do that. We usually find that whatever made us think of doing  
so is not the best design, and try another direction. If you could  
give us a more concrete example, we might be able to help you better.

S.

On 23 Oct 2009, at 14:32, Hr Borisov wrote:

> I have the following question: When we have a local object for a  
> method and we
> invoke a constructor for that object, can we catch the invocation to  
> the
> constructor and mock the creation of the object?
> I know that I can make a mock of the invocation of some method in a  
> class not
> depending on the reference but it would not help me. For example if  
> I want to
> mock isEmpty() method of some collection object I could not because  
> I can't
> calculate the consecutive number of the invocation that is important  
> to me.
> Thanks in advance!
>
> Example:
>
> Class A {
>  void someMethod() {
>    B ref = new B();
>
>    if (ref.doSomething() == 10) {
>      // I want to get here by mocking ref
>    }
>  }
> }
>
> Class B {
>  int doSomething() {
>   ...
>  }
> }
>

Steve Freeman

Winner of the Agile Alliance Gordon Pask award 2006
Book: http://www.growing-object-oriented-software.com

[phone]
M3P Limited.  http://www.m3p.co.uk
Registered office. 2 Church Street, Burnham, Bucks, SL1 7HZ.
Company registered in England & Wales. Number 03689627




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