Automating acceptance tests with BDD

I think we’re now running a pretty well-structured agile process, but one area that I’m interested in tightening up is how to express acceptance tests for user stories, and ideally how to automate the tests. A lot of the agile reading material talks in passing about acceptance tests without any real definition of the vocabulary or approach to use in expressing, organising and executing tests.

This fits in very nicely with some of the ideas in Behaviour Driven Design, which is like the next iteration of thinking around TDD. The idea is to express acceptance tests using a simple DSL vocabulary working in plain English, then hook up each acceptance test scenario to some automated tests which prove the scenario works as expected.

A simple example would be…

+Title: Customer withdraws cash+
As a customer,
I want to withdraw cash from an ATM,
so that I don’t have to wait in line at the bank.

In BDD, an acceptance test would be along the lines of…

+Scenario 1: Account is in credit+
Given the account is in credit
And the card is valid
And the dispenser contains cash
When the customer requests cash
Then ensure the account is debited
And ensure cash is dispensed
And ensure the card is returned

I’ve lifted the example here from the key article published on BDD from Dan North – if you’re interested so far then you should stop reading now and go and check out the article.

BDD frameworks will then map each step expressed in the text above through to a method in a test class, so you have a great balance between expressing the acceptance tests in simple language, but having the ability to execute the tests.

I found the best way to learn about this so far was a TekPub video – you’ll need a subscription, but the video is under the ‘Concepts’ section > Concepts:5 Behaviour-driven Design with Specflow.

Overall it seems like a more natural way to approach proving the application behaviour, and makes it much easier for testers and analysts to work alongside you in defining acceptance tests. I’m quite keen to roll this into our day-to-day process.