Nunit and PropertyConstraint

The PropertyConstraint of nunit is useful to assert some condition on a property of an object. This constraint permits to specify the Name of the property and then a constraint on his value. The only thing that miss is a better error message when the object does not contains the specified property. Suppose you write a wrong test like this

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[Test]
public void TestErrorMessages() {
   List<SimpleTwoProps> list = CreateTestList();
   Assert.That(list, new PropertyConstraint("PropB", new EqualConstraint(2)));
}

This test will fail because the List does not have PropB property, the error from nunit is.

*Expected: Property “PropB” 2

But was:  <System.Collections.Generic.List`1[SimpleTwoProps]>*

This sounds not so interesting to me, it could be better to modify the WriteActualValueTo

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public override void WriteActualValueTo(MessageWriter writer) {
   if (this.propertyExists) {
      writer.WriteActualValue(this.propValue);
   }
   else {
      writer.WriteActualValue(String.Format("The property {0} was not found on type {1}", name, base.actual.GetType()));
   }
}

With this modification the error is much more clear

Expected: Property “PropB” 2

But was:  “The property PropB was not found on type System.Collections.Generic.List`1[SimpleTwoProps]

This message is much more clear for me.

Alk.

Tags: Nunit Testing