NUnit: Dictionary Assert

Try using CollectionAssert.AreEqual or CollecitonAssert.AreEquivalent.

Both will compare the collection's items (rather than the collection's reference), but as discussed before, The difference is the item's order within the collections:

• AreEqual - The collections must have the same count, and contain the exact same items in the same order.
• AreEquivalent - The collections must contain the same items but the match may be in any order.

Have a look at CollectionAssert.AreEquivalent. This will assert that the two dictionaries have the same contents, but are not necessarily the same instance.