Re: 100%% Method Testing and Generating Unit Tests

> Hey David,
>
> I'm going to go over some obvious stuff, which you
> already know, just for clearity.
>
> I tried to start with something really simple that
> represents everything we do when coding, which is
> mapping inputs to outputs and storing those inputs and
> outputs in tighthy little slots on objects.
>
> So in that example we have two slots.
>
> Let me just define a slot as something that can
> contain everything allowed/understood by a computer.
>
> Then we constrained the slots by making them int.
>
> Now they can only contain the subset of all values
> allowed that are int.
>
> So now we apply an Operation to the slots and put the
> result in a different slot.
>
> So we have a Class that with private int a,b,c
> and
>
> an Operation defined in
> Java
>
> public int multiply(int a, int b)
> return aXb;
>
> It does not really matter what that Operation is, the
> only thing we care about is that it correctly maps the
> inputs to the outputs.
>
> So lets start with the inputs.
>
> They have already been constrained.
>
> But is it done or is it possible that we need to
> constrain variable b further, to satisfy a API
> contract definition.
>
> For instance b must be between 100 and 200.
>
> Quick side note(If an EMF model contained all the
> variables, a, b, c, etc.) and we needed to place
> constraints on a int datatype like this, we could use
> an invarient constraint for that.
>
> OK - Back to the logic.
>
> So we constrain b further so that  100 < b < 200.
>
> So now we are wondering whether our method works?
>
> By looking at the constraint for a&b, being that "a"
> is an int, and "b" is a further constrained int,
>
> and the mapping the method performs we know all the
> possible return values.
>
> We also know all the possible input values.
>
> But we don't want to test every single input to
> output...
>
> 101X1, 102X1, ...
>
> So which ones do we test?
>
> Let's start with the assuming that were always going
> to pass legal values.
>
> So we want to test the type constraint on a and b,
> being int.
>
> So lets just assume that on the platform we are
> running legal values are
>
> -2222222222222222222 to 2222222222222222222
>
> So we use these two end of range values.
>
> And we test
>
> 101 and 199 for b, since that represents b's set of
> edge points.
>
> So the combinations we want to test for any
> mathematical operations with these two parameters are:
>
>  b              a
> 101 X -2222222222222222222
> 101 X 2222222222222222222
> 199 X -2222222222222222222
> 199 X 2222222222222222222
>
> If X works the way it's supposed to, then these tests
> should pass.
>
> Also, we test
>  b              a
> 99  X -2222222222222222222
> 99  X 2222222222222222222
> 201 X -2222222222222222222
> 201 X 2222222222222222222
>
> These should not pass.
>
> Then we assume that all other values are taken care
> due to the definition of X.
>
> So were did we get the
>
> 99,201,199,101,2222222222222222222,-2222222222222222222
> values from.
>
> Lets think of a and b as being datatypes.
>
> b is just a new datatype that can only
> have values between 100 and 200.
>
> So a DataType is just meta data defining an allowed
> set of values...which is where EMF or Java reflection
> comes in.  You would use them to analyze the meta data
> defined for a type.  Then combine that with knowledge
> of operators to generate test cases.
>
> Does that make more sense?
>
> Cheers,
> - Ole
>
>
>
>
>
>
>
>
>
>
> --- David Saff <saff@...> wrote:
>
> > Ole,
> >
> > I'm getting my head around your suggestions.  (At
> > least) one thing is
> > tripping me up:
> >
> > On 12/31/06, Ole Ersoy <ole_ersoy@...> wrote:
> > > "What does it mean for a method to be 100% unit
> > > tested?"
> > >
> > > For instance suppose there's a method
> > >
> > > public int multiply(int a, int b)
> > >
> > > return aXb;
> > >
> > > Do we unit test this?
> >
> > Do we write this in the first place?  Perhaps
> > another example would
> > help me more.
> >
> >    David Saff
> >
>
>
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