nunit-core team mailing list archive

["Charlie Poole" <charlie@xxxxxxxxx>]

It's a bad idea to have constraints fail when they are used improperly.

If you do that then...

Constraint c = new NonReusableConstraint(...);
Assert.That( actual, c ); // This fails
Assert.That( actual, new NotConstrant( c ) ); // This succeeds!

In an earlier version of NUnit we had this problem when using
a constraint that expects a collection with a non-collection.
The constraint was failing but its negation would succeed.
Now we throw an ArgumentException in this sort of situation.

In the case of a non-reusable constraint we could throw an
exception, but only if the constraint "knew" it was being
reused. 

Charlie

> -----Original Message-----
> From: 
> nunit-core-bounces+charlie=nunit.com@xxxxxxxxxxxxxxxxxxx 
> [mailto:nunit-core-bounces+charlie=nunit.com@lists.launchpad.n
> et] On Behalf Of blaz
> Sent: Friday, March 05, 2010 3:16 AM
> To: nunit-core@xxxxxxxxxxxxxxxxxxx
> Subject: [Nunit-core] [Bug 532488] Re: constraintsfrom 
> ConstraintExpression/ConstraintBuilder are not reusable
> 
> In some rare cases reuse could be useful.
> Main problem is that I was unable to find any documentation 
> specifying that constraints should not be reused, or that 
> constrains supplied by NUnit are not reusable. Actually in 
> most cases under most conditions constraints are reusable.
> 
> I think that this bug could be fixed either by making 
> constrains reusable or by placing appropriate warning in 
> documentation 
> (http://www.nunit.org/index.php?p=constraintModel&r=2.5.3), 
> or constrains that are not reusable should fail on reuse.
> 
> --
> constraints from ConstraintExpression/ConstraintBuilder are 
> not reusable
> https://bugs.launchpad.net/bugs/532488
> You received this bug notification because you are a member 
> of NUnit Developers, which is subscribed to NUnit V2.
> 
> Status in NUnit V2 Test Framework: New
> 
> Bug description:
> Constraint that I receive from syntax helper (Is.Not.Null) is 
> not reusable, but I guess this is more general problem.
> I found this problem when upgrading nunit.framework.dll from 
> v2.4.6 to v.2.5.3. In both cases tests were executed witn 
> NUnit 2.5.3 console.
> Worst thing about this problem seems that tests could 
> actually pass when they should fail if you reuse constraint.
> 
> Here is simple example that demonstrates the problem:
> 
> using NUnit.Framework;
> using NUnit.Framework.Constraints;
> 
> namespace NUnit_2_5_3_bug
> {
>     [TestFixture]
>     public class FailToReuseConstraint
>     {
>         /// <summary>
>         /// Constraint from <see cref="ConstraintExpression"/>.
>         /// </summary>
>         /// <remarks>
>         /// Demonstrates that constraint received from syntax 
> helper is not reusable.
>         /// </remarks>
>         [Test]
>         public void FromSyntaxHelper()
>         {
>             Constraint expression = Is.Not.Null;
>             Assert.That(this, expression, "one");
>             Assert.That(this, expression, "two"); // this 
> step fails on NUnit.2.5.3
>         }
> 
>         /// <summary>
>         /// How NUnit 2.4 did it (i think).
>         /// </summary>
>         [Test]
>         public void NotConstraint()
>         {
>             Constraint expression = new NotConstraint(Is.Null);
>             Assert.That(this, expression, "one");
>             Assert.That(this, expression, "two");
>         }
>     }
> }
> 
> 
> 
> _______________________________________________
> Mailing list: https://launchpad.net/~nunit-core
> Post to     : nunit-core@xxxxxxxxxxxxxxxxxxx
> Unsubscribe : https://launchpad.net/~nunit-core
> More help   : https://help.launchpad.net/ListHelp
>