how to: extract interface of class with methods from a superclass

"Donaldson, John" <[email protected]> Fri, 20 Sep 2013 16:55:08 +0000
Newsgroups gmane.comp.programming.refactoring
Message-ID <716D07F3CBA94244A0922E7A99837C3A109FB62E@G5W2715.americas.hpqcorp.net>
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I have a class (legacy code) - let's call it C, which uses methods on class=
 B.
To make testing easier I could "extract interface" of B and create a test f=
ake of it.
Except, class B inherits class A and C is calling one of the inherited meth=
ods.

Something like this:
   Class A{
      MethodOfA(){ ... }
   }

   Class B inherits A{ ... }

   Class C{
      B myB;
      MethodOfC(){
         myB.MethodOfA();
      }
   }

Quite rightly "extract interface" on B only gives me the methods on B.
So, how to separate C from B abd A for testing purposes?

What's the good/correct/elegant refactoring?

John D.

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<div class="WordSection1">
<p class="MsoNormal">I have a class (legacy code) &#8211; let&#8217;s call it C, which uses methods on class B.<o:p></o:p></p>
<p class="MsoNormal">To make testing easier I could &#8220;extract interface&#8221; of B and create a test fake of it.<o:p></o:p></p>
<p class="MsoNormal">Except, class B inherits class A and C is calling one of the inherited methods.<o:p></o:p></p>
<p class="MsoNormal"><o:p>&nbsp;</o:p></p>
<p class="MsoNormal">Something like this:<o:p></o:p></p>
<p class="MsoNormal">&nbsp;&nbsp; Class A{<o:p></o:p></p>
<p class="MsoNormal">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; MethodOfA(){ &#8230; }<o:p></o:p></p>
<p class="MsoNormal">&nbsp;&nbsp; }<o:p></o:p></p>
<p class="MsoNormal"><o:p>&nbsp;</o:p></p>
<p class="MsoNormal">&nbsp;&nbsp; Class B inherits A{ &#8230; }<o:p></o:p></p>
<p class="MsoNormal"><o:p>&nbsp;</o:p></p>
<p class="MsoNormal">&nbsp;&nbsp; Class C{<o:p></o:p></p>
<p class="MsoNormal">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; B myB;<o:p></o:p></p>
<p class="MsoNormal">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; MethodOfC(){<o:p></o:p></p>
<p class="MsoNormal">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; myB.MethodOfA();<o:p></o:p></p>
<p class="MsoNormal">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; }<o:p></o:p></p>
<p class="MsoNormal">&nbsp;&nbsp; }<o:p></o:p></p>
<p class="MsoNormal"><o:p>&nbsp;</o:p></p>
<p class="MsoNormal">Quite rightly &#8220;extract interface&#8221; on B only gives me the methods on B.<o:p></o:p></p>
<p class="MsoNormal">So, how to separate C from B abd A for testing purposes?<o:p></o:p></p>
<p class="MsoNormal"><o:p>&nbsp;</o:p></p>
<p class="MsoNormal">What&#8217;s the good/correct/elegant refactoring?<o:p></o:p></p>
<p class="MsoNormal"><o:p>&nbsp;</o:p></p>
<p class="MsoNormal">John D.<o:p></o:p></p>
</div>




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