Behaviour-driven development (BDD) is an Agile software development methodology that designs applications based on business requirements. It focuses on the application's overall behaviour, which the end user expects to encounter during use. BDD is derived from Test-driven development, where the testing is conducted before writing production code. In BDD, however, the application's expected behaviour is mapped out first, and the code is written to represent those behaviours.
One defining feature of BDD is that the code is written in plain English text rather than in complex programming languages. This aims to make it easier for non-technical team members and stakeholders to understand feedback and give more input.
Behaviour-driven development helps development teams avoid bulky code and unnecessary features while promoting a focus on a specific outcome and absolute parity between technical and non-technical teams, business professionals and engineers. This methodology is an extension of TDD, sharing most of its features, principles and advantages. Where TDD seeks to build the product accurately, BDD aims to build the accurate product.
In software development, framework principles are rules or beliefs that serve as basic guidelines for operations. They are a collection of philosophies, approaches, methods and industry best practices, which ensure a smooth running and efficient software development process. BDD is no different and has its foundation laid on three basic principles. They are:
Enough is enough
This means just enough time is put in for the project to start. Anything more would be considered a waste. It also means ample time should be given to planning, testing and development. "Enough is enough" implies imputing only the right amount of time required, nothing more, but just as importantly, nothing less.
Deliver stakeholder value
The sole aim of any software development life cycle is to deliver value to the stakeholders. Value, in this case, means solving the client's problems or achieving the client's goals through efficient and secure applications that meet their requirements. Requirements should be critically analysed to ensure that every operation undertaken is valuable to the client, avoiding wasting time and resources.
Focus on behaviour
BDD is more concerned with how the product should behave during use than its structure. This principle embodies the very nature of the BDD framework.
A BDD life cycle typically begins with a conversation between the developers, product owners, and customers to create a picture of how the product should function. These desired behaviours are then laid out as objectives for the developers. Test cases are written out of the requirements, and if the product passes the behaviour tests, it is deemed ready for conveyance to the client.
Behaviour-driven development revolves around conducting behaviour-specific tests or functional specifications that outline executable scenarios for the application.
Before implementing BDD:
When gathering requirements in BDD, we usually encounter a language called Gherkin.
Gherkin is a domain-specific language that defines business behaviour without detailing its implementation. It uses plain English to define tests for better understanding among non-technical members and teams.
Most BDD tests are written in Gherkin. BDD frameworks not using Gherkin use non-Gherkin domain-specific languages (DSLs) with BDD-like features.
Some keywords commonly encountered in Gherkin are:
Feature: describes software features.
Scenario: describes patterns such as events, required results, and initial context.
Background: describes the context and background of the system with particular features and solutions.
Scenario Outline: describes the outline of the system behaviour.
Examples: describes factors relevant to BDD, such as features, solutions, functionalities, and others.
Gherkin testing is broken down into a "Given-When-Then" formula construct. This formula defines behaviour in the following ways:
These three steps are parsed and executed by the BDD framework and are sometimes called automated acceptance tests. To expand on this, we will delve into different approaches to implementing BDD frameworks.
This focuses on testing the product at the right time to ensure how efficient it is in real time.
It bypasses traditional development and testing limitations, where errors and vulnerabilities are discovered after deploying the product.
Agile testing approach
Behaviour-driven development focuses on Agile testing rather than following the traditional build, test, and fix errors procedure. Agile testing uses iterative development and testing methodology that emphasises collaboration between customers and development teams.
Built-in quality approach
BDD follows a built-in quality approach, ensuring that the product meets all requirements.
BDD framework involves three main stages: discovery, formulation, and automation.
This is the first phase of the behaviour-driven development framework, where the acceptance criteria are researched and decided.
The acceptance criteria are based on product type, key features, target audience, present market, and other factors. This behaviour-driven development requires the collaborative input of all team members to come up with the acceptance criteria.
The formulation phase is mainly relevant when a backlog item is just about to get implemented. The basic purpose of this phase is to ensure that the acceptance criteria are confirmed and ready to be applied in real time. Acceptance tests in the formulation phase execute this part.
The purpose of acceptance testing is to run quality assurance methods to determine whether an application or product is as per the requirements. It decides to what extent or degree you can accept a product based on end-user needs and approval. As such, the formulation phase is dedicated to turning the initial acceptance criteria into a stable version with less ambiguity or flaws.
The Automation phase automates the process of acceptance tests. Here, acceptance tests are automated and then run to determine if the new behaviours are compatible with the system.
To rightly implement BDD framework, one must be familiar with the BDD tools. Below, we discuss three top BDD tools: Cucumber, Gauge and JBehave.
Cucumber: Cucumber is an open-source testing BDD framework that enables developers to write requirements in Gherkin. This language allows anyone to read and understand the information easily. It supports several programming languages, including Ruby, Java and .NET, and software platforms like Ruby on Rails, Selenium and Spring Framework.
Gauge: Gauge is a cross-browser, open-source test automation framework. It works with multiple programming languages and integrates with several integrated development environments and continuous integration servers, including IntelliJ and Jenkins.
JBehave: This is an open-source BDD framework designed for microservices testing and Java-based development. While JBehave is restricted to Java implementations, it offers many customisation options for developers to configure their BDD tests.
Behaviour-driven development closes the gap between developers and businesses by making implementation as close to the behaviour as possible. It enforces good structure and layers for automation. In a nutshell, BDD is unique because it can be easily understood by non-technical individuals and focuses on collaborating with business organisations.
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