Tuesday, April 9, 2013

An Organization and Structure for Data-Driven Testing

This post follows up on the one from yesterday:

So, data-driven testing is the way to go for a huge return on finding and regressing product issues and measuring the whole quality picture. How to start?

I like XML files to do this. Here are some reasons:

1.       Your favorite text editor will work for reviewing, editing, and extending your test set.

2.       If given values for a test are optional and you provide defaults as needed, the XML can be “sparse” and even easier to read and edit. The data that drives the test also expresses the focus and reason for the test, in the data itself!

3.       You can be as constrained or as loose with the data schema (the layout of the XML data) as you want.

4.       Extending your data engine can be as simple as allowing and parsing different values. For example, for testing with objects that include pointers or references, you can put “null” as a value in your XML and have your engine parse and use that for the test, in the context as defined in the XML.

There are many engines that help with data-driven tests, or with some time and skill, you can write your own.

To make the tests more readable and extensible, use different XML files to drive different kinds of tests – e.g. positive vs. negative tests, scenario A vs. scenario B, vs. scenario C. With appropriate labels, comments, error messages and bug numbers inline with the data for the individual test, all your tests can be self-documenting and even self-reporting, freeing you from maintaining documents with details about the tests and removing that source of errors and potential conflicts.

A relational database is a more powerful way of handling large amounts of structured data. This would be a better choice for example if you were doing fuzz testing by generating large numbers of tests, according to your randomization scheme, and then saving to and executing from a SQL database. Even with fuzz testing, it’s very important that tests be as repeatable as possible!


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