Mar 19 2013
BDD, Feature File & Gherkin Syntax
Behaviour Driven Development a.k.a BDD enforces agile team to write human readable, executable specification. Gherkin is a very nice Domain specific Language which support human readable syntax in different languages. BDD is all about bridging communication gap so writing better feature file is a key to success in the BDD projects.
Once you have all necessary communication with business, next step is to write feature files. Ideally, QA should take lead to write down all scenarios, preconditions and expected results in the form of feature files. Business analysts / product owners or even scrum masters can contribute to feature files. Once the team agrees all possible scenarios have been covered, then developers can kick start implementation.
Few tips to write better feature files
1. Use Background
Gherkin is a Domain Specific Language used to describe features in the ‘GivenWhenThen’ format. Gherkin has some cool features in order to avoid duplication or repetitive steps. Gherkin helps readability for business users. Proper use of the ‘background’ feature of Gherkin can help to avoid repetitive tasks in each scenario. It is not mandatory to use ‘background’ in each and every feature, but it makes the feature file more readable. There are few things you need to keep in mind while using ‘background’. You have to keep your background section very short, just enough to keep the scenario in context. You shouldn’t include technical stuff like starting some services, clearing cache, launching browsers in the background, as the reader will assume these things. You’ll implement this in the step definitions by using proper hooks.
2.Use of Data Tables, Examples, Doc String, Multiple tables of example & nested steps
Gherkin provides ability to enhance your feature files by using tables. You can use ‘Data Tables’. Data tables allow you to set-up certain set of data as a pre-condition for the tests (Given) or as an example in assertions (Then). You need to use ‘Scenario Outline’ to extend feature files by examples. Doc String is another cool feature of Gherkin which allows you to hard-code ‘text’ into your feature files e.g. you can write email message in the quotes as an assertion. Gherkin also allows you to specify multiple tables of examples. Nesting Steps means hiding the implementation details.
3.Use tags and Sub-folders to organise features
Tagging the features/scenarios with certain tags helps categorise them into different groups. You can apply a filter to run the features/scenarios with specific tags. You can also create sub-folders according to the functionality to organise features effectively.
Here is an example feature file covering almost all the above mentioned points:
Feature: Login In order to secure my website , as a business owner , I want to implement login functionality Background: Given I am on login page @wip @smoke @browser @ci Scenario Outline: Check user's login credentials Given I filled <username> <email> and <password> When I clicked on Login Then I should see <success or failure> message a And I should get an email saying: "Dear User, You have just tried to login to our system. If your login is successful then you will get another email to verify you details. Thanks " Examples: Valid login |username |email |password |success or failure | |Andy |firstname.lastname@example.org |abcd1234 |success | |Mike |email@example.com |abcd1234 |success | Examples: InValid login |username |email |password |success or failure | |Andy |firstname.lastname@example.org| |failure |
The key benefits of Behavior-Driven-Development (BDD) practices are communication enhancement and customer satisfaction which can be achieved by better communication & better feature files. Hope you find these feature writing tips useful.
Happy BDD !