MbUnit: Testing custom ordered collection

Question

I have a custom collection type of data. This data is sorted by three properties in their order, e.g. take the following example:

class Data
{
  public int PropertyA() { get; set; }
  public int PropertyB() { get; set; }
  public int PropertyC() { get; set; }
}

The collection must maintain the order of A, B, C, e.g.:

[A, B, C]
[1, 2, 5]
[1, 3, 3]
[1, 3, 4]
[1, 4, 1]
[2, 1, 2]
[3, 3, 1]
[3, 4, 2]

I'd like to write some tests to ensure that this order is maintained in the collection through the usual suspect Add and Remove operations. I'm using Gallio and MbUnit 3, and I think there must be an easy way to do this with their attributes, I just don't get it right now. Any ideas?

Answer 1

MbUnit v3 has a new useful Assert.Sorted method. You just need to pass the enumeration instance to evaluate. If the enumerated objects implements IEquatable, then everything is automatic.

[Test]
public void MySimpleTest
{
   var array = new int[] { 1, 5, 9, 12, 26 };
   Assert.Sorted(array);
}

Otherwise, you still have the possibility to specify a custom comparison criterion (with the new handy structural equality comparer, for example).

[Test]
public void MyComplexTest
{
   var array = new Foo[] { new Foo(123), new Foo(456), new Foo(789) };
   Assert.Sorted(array, new StructuralEqualityComparer<Foo>
   {
      { x => x.Value }
   });
}

Have a look at the Gallio/MbUnit API doc reference for more details.

Answer 2

Yann Trevin has been working on a "CollectionContract" for MbUnit v3. I don't think it can handle ordered collections right now but I'm sure he'd be interested in adding that capability given an appropriate comparison delegate to describe the ordering invariant.

You'll find a example of this in the "SampleCollectionTest" fixture of the MbUnit.Samples project in MbUnit v3.0.6.

I recommend that you post your idea to the mbunitdev mailing list where he'll see it: http://groups.google.com/group/mbunitdev

Answer 3

In MbUnit v2, you could use CollectionOrderFixture.. can't find it it MbUnit v3 though