public virtual void when_I_set_existing_property_then_I_can_use_dynamic_property_syntax() { string original = getExistingPropertyDynamic(Properties); setExistingPropertyDynamic(Properties, "Foo"); string changed = getExistingPropertyDynamic(Properties); Assert.NotEqual(original, changed, "Existing property value was not changed by {0} on {1}", this.GetType().Name, ProjectFile); Library.Save(); var saved = XDocument.Load(ProjectFile) .Root .Descendants(MsBuildXmlNs + existingPropertyName) .Select(e => e.Value) .First(); Assert.Equal("Foo", saved); }