Re: Testing a package's internal details.

[Stephen Leake <stephen_leake@stephe-leake.org>]

"Peter C. Chapin" <pcc482719@gmail.com> writes:

> A situation has come up for me and I'm wondering what the "best" way is to
> handle it. Here are the particulars...
>
> I have a package that models a single abstract object. The specification
> declares the operations that are allowed on the object. I would like to write
> some test procedures that can be used to exercise my implementation. Using a
> test program that exists outside the package, I can treat the package like a
> black box and call the public interface to the package during my tests. That
> is fine.

Ok so far.

> However, I'd also like to write some test procedures that independently
> exercise certain internal facilities without being constrained by the public
> interface. Those procedures are not really part of the abstraction I'm trying
> to present and I don't really want normal client code to call them. I do want
> the test program to call them, of course.
>
> Is there a "best practice" in this area that I should be following? At first I
> thought I might be able to make my test procedures part of a child package
> but that doesn't work because a child package has no access to the internal
> part of the parent's body (true?). 

Right.

> I suppose I could declare the test procedures in the private part of
> the parent's specification and then provide a child with a public
> procedure that just calls the parent's private test procedure.

Better to make the actual operations visible in the private part:

package Test_Me is
  -- ...
private
  procedure Private_Op_1;
  function Private_Op_2 return string;
end Test_Me;

package Test_Me.Tester is
  procedure Test_Private_Op_1;
  procedure Test_Private_op_2;
end Test_Me.Tester;

Or, if the private ops are fairly complicated, and use complicated
types, move them to a separate private package:

package Test_Me is

end Test_Me;

private
package Test_Me.internals is
end test_me.internals;

with test_me.internals;
package body test_me is

    -- stuff that uses test_me.internals

end test_me;

private
package test_me.internals.tester is

...
end test_me.internals.tester;

To work with a framework like AUnit, you sometimes have to declare a
public access package:

package Test_Me.internals_aux is

    procedure private_op_1; 

end test_Me.internals_aux;

Test_Me.internals_Aux.private_op_1 calls the real
test_me.internals.private_op_1.

-- 
-- Stephe