One problem that comes to mind is that you can easily make assumptions
about what is likely to change in your code, and test that, but its
harder to guess what will change in your dependencies.

Of course, that which changed on you before should be suspect, and test
anything that's considered alpha, so its not impossible...

Daniel

Andreas Raab <andreas.raab at gmx.de> wrote:
> Hi Stef,
> 
> Thanks for the info. One thing I am wondering about is the following. When
> we write tests, we typically model our "internal assumptions" quite
> precisely which helps us to track may of the problems that occur when those
> assumptions (even slightly) change. Is there anything in research that
> explains why we don't do this on the environment? Is it just considered too
> big a task? Or is it that we merely assume that we have an unchanging target
> (which requires people/vendors to fix the API once and forever)? Or is it
> that - because in many cases we simply don't know enough about the
> environment (black box reuse) - we don't even know what assumptions we (and
> the environemnt itself) is making? What I am interested in here is to
> understand what the causal effect(s) for our effectively blindly relying on
> the environment is.
> 
> Just curious,
>   - Andreas
> 
> > -----Original Message-----
> > From: squeak-dev-bounces at lists.squeakfoundation.org 
> > [mailto:squeak-dev-bounces at lists.squeakfoundation.org] On 
> > Behalf Of ducasse
> > Sent: Wednesday, November 05, 2003 9:06 AM
> > To: The general-purpose Squeak developers list
> > Subject: Re: "Environment tests"
> > 
> > 
> > Hi andreas
> > 
> > Even with Java or languages with a static type system, 
> > nothing prevents
> > you that your system will break. There are a lot of research 
> > papers on 
> > that and none
> > provide a good solution. Between one version and another one the same 
> > interface
> > can hold but the behavior slightly changes and break everything 
> > (fragile base problem for example).
> > 
> > The minimal first step would be to be able to rely on well-known and 
> > identifiable versions of other components (package).
> > 
> > Stef
> > 
> > On Mercredi, nov 5, 2003, at 08:32 Europe/Zurich, Andreas Raab wrote:
> > 
> > > Hi Guys,
> > >
> > > Here's a weird and somewhat OT thought that was triggered by a 
> > > discussion I
> > > had today. One of the things I am noticing when looking at 
> > SqueakMap 
> > > (and my
> > > use of it) over the last year is that many of the packages that are
> > > available from SM tend to break in the face of later Squeak 
> > versions. 
> > > What
> > > happens? Effectively, these packages have been written under the 
> > > assumptions
> > > of a certain environment in which they exist (namely that of Squeak 
> > > X.Y) and
> > > if these assumptions are ever (even partially) invalidated 
> > they break.
> > >
> > > In the discussion I had today Alan (again) mentioned that 
> > one of the 
> > > things
> > > that could be done for making sure an object (or a package) can 
> > > survive in
> > > some environment is to model (at least some) of the 
> > assumptions about 
> > > the
> > > environment explicitly. We do this internally by, for 
> > example, using 
> > > unit
> > > tests for the package but typically we have no model 
> > whatsoever about 
> > > our
> > > environment. This is (at least I think so) an even larger 
> > problem for a
> > > dynamically typed environment than it is for a statically typed 
> > > environment.
> > > In the statically typed environment you can at least be 
> > assured that 
> > > the
> > > compiler will do certain checks on your types (and 
> > messages) so unless 
> > > the
> > > semantics of some message (or type) changes you should be safe (in 
> > > theory).
> > >
> > > What I'm curious about here is: Has anyone ever seen a 
> > (hopefully even
> > > usable ;) approach to model "environmental assumptions"? 
> > Are there any
> > > common rules/guidelines on which "environment tests" could be based?
> > > Anything else in this area?
> > >
> > > Cheers,
> > >   - Andreas
> > >
> > >
> > >
> > 
> >