Is there any point Unit testing serialization?

Question

I have a class that serializes a set of objects (using XML serialization) that I want to unit test.

My problem is it feels like I will be testing the .NET implementation

Answer 1

In my experience it is definitely worth doing, especially if the XML is going to be used as an XML document by the consumer. For example, the consumer may need to have every element present in the document, either to avoid null checking of nodes when traversing or to pass schema validation.

By default the XML serializer will omit properties with a null value unless you add the [XmlElement(IsNullable = true)] attribute. Similarly, you may have to redirect generic list properties to standard arrays with an XMLArray attribute.

As another contributor said, if the object is changing over time, you need to continuously check that the output is consistent. It will also protect you against the serializer itself changing and not being backwards compatible, although you'd hope that this doesn't happen.

So for anything other than trivial uses, or where the above considerations are irrelevant, it is worth the effort of unit testing it.