RE: [MO-java-users] How to 'mock' object with static method?

[<DeS...@em...>]

Herman,

> (1) Listing : The class under test
> 
> class MyClass {
> 
>       // ----
>       public void myMethod () {
>             // .. Blah ...
>             MyBackEndClass.callStaticMethod () ;
>             // ^^^ i want to mock this object
>       }
> 
> }
> 
> What i want to do is to create a mock object, say 
> MockMyBackEndClass and call a method (static?) on it, 
> thus avoiding actual call to backend. The problem is that 
> i cannot override static method. So even if i subclass
> MyBackEndClass to create a MockMyBackEndClass,
> MockMyBackEndClass.callStaticMethod() will always call 
> implementation in MyBackEndClass ...
> If the method callStaticMethod were not static, it's quite 
> straightforward to substitute actual MyBackEndClass to 
> MockMyBackEndClass in the test code... but it isn't  ... :-(

I think you are out of luck. In this case, I would try to refactor
MyBackEndClass so I can call an instance method. I suspect MyBackendClass
implements some interface like MyBackendInterface, otherwise you wouldn't be
able to mock it. My approach would be to decouple the retrieval of the
back-end object from the method that uses this object. Something like this:

class MyClass {

      // ----
      public void myMethod () {
           this.myMethod(BackendLookup.getBackendObject());
      }

      protected void myMethod(MyBackEndInterface backendObject) {
            // .. Blah ...
            backendObject.callInstanceMethod () ;
            // .. More blah ...
      }
}

You can then write unit tests for myMethod(MyBackEndInterface) providing the
mock version as an argument. I also assume that you write other unit tests
for the BackendLookup class.

Ringo