Theories on Gary Evans website

Theory driven development using Microsoft Pex Explorer

Sun, 11 Jan 2009 00:00:00 +0000

EDIT: NOTE that some of the contents of this post have been recently been edited thanks to great feedback from Peli de Halleux (http://blog.dotnetwiki.org/). He pointed me at a great post on Test Driven Development with Parameterized Unit Tests that he’d wrote here: http://blog.dotnetwiki.org/TestDrivenDevelopmentWithParameterizedUnitTests.aspx

I’ve been playing with Microsoft Pex to try out some theory-driven development. I’ve found it a great tool – actually much better than I was hoping, it’s found more bugs, and test cases, than using just unit testing or TDD (Test-Driven Development). It’s test-driven development on steroids!

Comparing Theories to more traditional testing

Wed, 19 Mar 2008 00:00:00 +0000

My old work colleague Tim has recently blogged about using NSpec to specify a stack.

NSpec has the same sort of functionality as a unit testing framework such as NUnit. The terminology has been changed to get over the roadblock that some people have in adopting tests.

Theories actually give something over and above normal unit testing, and that’s what I’m going to look at in this blog post. I’m going to look at Tim’s example and show how using theories actually differ from Tim’s more traditional example.

Sample Theory Implementation as NUnit Extension.

Wed, 19 Mar 2008 00:00:00 +0000

There’s been lots of comments bouncing around on the NUnit mailing list about what exactly constitutes a Theory, and what the desired features are, so I’ve created an NUnit extension with a sample Theory implementation - you can get it, Maslina version 1.0.0.0, from www.taumuon.co.uk/rakija

xUnit.Net implements theories but does not have any in-built Assumption mechanism (you can effectively filter out bad data, which is the same as a filtering assumption). JUnit 4.4, I think, only filters out data - it doesn’t tell us anything about the state of an assumption.

Theories

Thu, 13 Mar 2008 00:00:00 +0000

I’ve just released a slightly updated version of my NUnit extension for data-driven unit testing.

There’s been a lot of discussion on the NUnit developer list recently regarding Theories - something new in JUnit and xUnit.Net, and it’s taken a while to discover why they’re so powerful (they’re superficially very similar to data-driven unit tests, and a lot of the differences are semantics).

First, there’s some good background on theories written by David Saff:
http://shareandenjoy.saff.net/tdd-specifications.pdf
http://shareandenjoy.saff.net/2007/04/popper-and-junitfactory.html
http://dspace.mit.edu/bitstream/1721.1/40090/1/MIT-CSAIL-TR-2008-002.pdf