Unit-testing – How to test a parser for a bespoke XML schema

parsingunit testing

I'm parsing a bespoke XML format into an object graph using .NET 4.0. My parser is using the System.XML namespace internally, I'm then interrogating the relevant properties of XmlNodes to create my object graph.

I've got a first cut of the parser working on a basic input file and I want to put some unit tests around this before I progress on to more complex input files.

Is there a pattern for how to test a parser such as this?

When I started looking at this, my first move was to new up and XmlDocument, XmlNamespaceManager and create an XmlElement. But it occurs to me that this is quite lengthy and prone to human error. My parser is quite recursive as you can imagine and this might lead to testing the full system rather than the individual units (methods) of the system. So a second question might be What refactoring might make a recursive parser more testable?

Best Answer

Create a separate test project, add a reference to your parser project, write your test class, and add your test document as an embedded resource (under "Build Actions"). In your test class, use Assembly.GetExecutingAssembly().GetManifestResourceStream('test-data.xml') to get your test data as a stream. You should be able to feed that stream to your parser and run your tests.

Related Solutions

C++ write own xml parser vs using tinyxml

Generating an XML file is a different task to consuming an XML file. If you're just generating an XML file in a specific format with fairly simple inputs, then it's not too much work to just do something like:

mystream << "<xmldata>" << endl;
mystream << "<something>Blah</something>" << endl;
mystream << "</xmldata>" << endl;

That's probably going to be much simpler than building a TinyXML object model, populating it and then writing it out.

The only thing you need to worry about is proper escaping (i.e. turning "&" into "&", "<" into "<" and so on).

Now, if you were parsing an XML file, then I would definitely recommend using a third-party library (and TinyXML is a good one if you don't need XSLT or schema validation, etc).

ANTLR vs Parsing Libraries – When to Use Each

You could use either to perform either task. The difference is what each is meant for. You can draw pictures or diagrams in Excel if you want to, but you can also draw a picture in something built for that purpose.

JSON and XML libraries are designed around general purpose loading of documents, pulling parts out of them, or transforming their structures into different structures, etc.

ANTLR on the other hand is a tool designed for generating parsers for compilers. It is tailored specifically to suit the needs of that task.

If you use an xml or json parser to parse either of those, you'll ultimately end up writing a bunch of code that transforms your input into an AST of some sort, for you to process. So, whether you want to write and debug all of that, or use something that gives it to you up front, that's up to you.

Best Answer

Related Solutions

C++ write own xml parser vs using tinyxml

ANTLR vs Parsing Libraries – When to Use Each

Related Topic