Behavior-driven testing (BDT) is a testing method in which the testing scenarios are based on user behavior. Often confused with BDD, BDT is based on the given-when-then structure, and enables better collaboration with the business and faster time-to-market. Let’s see which additional advantages BDT offers developers, when to use it and the recommended BDT tools. But first, let’s get a clearer picture of what BDT is.

What is Behavior-Driven Testing (BDT)?

Behavior-Driven Testing (BDT) is a software testing method that aims to test actual user behavior. Therefore, in BDT test scenarios are built according to the steps the user would take and not according to software functionality. In addition, BDT test scenarios are built in an understandable language. This enables clarity and communication with business stakeholders when creating and monitoring the tests. As a result, tests better reflect the users’ needs and the features can be released and delivered faster. Like many types of software testing, BDT can be automated by implementing the tests into the CI/CD workflow. 

BDT vs. BDD

Behavior-driven testing is often used interchangeably with behavior-driven development (BDD). However, they are not the same thing. Behavior-driven development is the software development approach that aims to develop software only according to user behavior. This helps avoid excessive code and unnecessary features. Like BDT, BDD is also based on conversations with business stakeholders and includes real user scenarios. However, unlike BDT, the goal of these discussions is for development, not for testing.

BDT Test Structure

The structure of BDT tests enables clearly understanding and defining the expected user behavior. Tests are divided into three parts:

Part 1 - The Context

This is the situation the user is in. For example, a user signed in, opened a webpage, or entered a string of characters.

Part 2 - The Event

The action the user took, which is being tested. For example, transferring money between accounts, creating a new entity, booking a flight, and more.

Part 3 - The Outcome

What is supposed to happen when the software functions correctly and the result is as expected. For example, the file downloads, a new page opens up, a form is submitted, etc.

A simpler way to remember this structure is “Given - When - Then”. Given the user signed in. When the user clicks on a button. Then a new page opens up. To avoid confusion, it is recommended to test only one scenario per test.

4 Behavior-Driven Testing Advantages

Behavior-driven testing provides many advantages to developers. These include:

1. Test Clarity

Behaviour-driven testing scenarios are built according to what the users will do in the product. As a result, when building the test scenarios, a lot of thought is put into what and what not to test, and what the expected results should be. This enables prioritization and creates clarity about the structure and purpose of the tests.

2. Collaboration Across the Organization

Using a simple logical structure (if-when-then) and human-readable language makes the tests and their logic easy to understand, both for developers and non-developers. This enables collaboration when discussing and writing tests. For example, the business stakeholders can write user stories to show the developers the software requirements. The result is faster time-to-market and less bugs for the users.

3. Relevant Testing Scope

By prioritizing tests according to what the user will do, tests will cover most common use cases. This ensures relevancy and enables tests to be focused on what the user needs, as well as covering all edge-cases. No resources are wasted.

4. Enable Automation

BDT tests can be integrated into the CI/CD pipeline and run automatically according to a predefined schedule. This enables agility and ensures developers can focus on future development.

When to Use Behavior-Driven Testing

There are many types of testing that can benefit from BDT. These include:

BDT with Integration Testing

Integration testing is the testing of different software modules together as a group, to ensure all modules can function together. BDT enables creating clear and accurate scenarios for these integrations, based on the users’ behavior and in their language.. Given the integration between the components, when a user performs a certain action, then the integrated components do X. Incorporating BDT into integration testing provides the flexibility and freedom to test cross-module scenarios to examine the system from end-to-end.

BDT with API Testing

A part of integration testing, API testing examines the functionality and reliability of the APIs in the business layer of the architecture. This makes BDT a really good fit for API testing. BDT scenarios enable clearly mapping each step into an API call that is being tested. It’s very easy to correlate each API call into a given-when-then step and write it down in clear words.

BDT for UI Testing? Consider rethinking

While some companies use BDT for UI testing, this is not a recommended best practice. The UI layer has multiple, complex scenarios. Each action could have thousands of outcomes. Even actions that seem similar could have a unique UI outcome, which would require a completely different set of tests. Therefore, writing UI tests down in the given-when-then structure and then in code is complicated and time-consuming.  In addition, such tests could also be very brittle, as the UI constantly changes. After all, BDT was created to test behavior, not visibility.

Behavior-Driven Testing Recommended Tools

There are many tools available for behavior-driven testing, which can be incorporated in an automation flow. Here are a few of the most recommended ones:

Cucumber

Cucumber is a popular BDT tool that uses Gherkin for writing tests. It reads executable specifications written in plain text and validates that the software does what those specifications say. Cucumber has a free open source version, as well as a paid version that offers more features. Cucumber supports multiple languages and provides reports for monitoring.

Karate

Karate is a Cucumber-based open source BDT framework for Java. It can be used for API testing, mocking, performance testing, and more. Karate is built on top of Cucumber, and shares some of the same concepts. One of these is the use of a Gherkin file, which describes the tested feature. However, unlike Cucumber, tests aren't written in Java and are fully described in the Gherkin file.

SpecFlow

SpecFlow is an open-source BDT framework for .NET. It can be used for REST API testing, mobile automation, desktop automation, and more. SpecFlow tests are written using Gherkin, which allows you to write test cases using natural languages. SpecFlow uses the official Gherkin parser, which supports over 70 languages.

Loadmill 

Loadmill’s BDT approach solves the regression testing challenge by automatically creating regression tests based on real user behavior. These tests are created by analyzing thousands of user recordings from all kinds of sources and processing them into automated back-end tests. Tests are based on real-world scenarios, ensuring that everything that worked for the users yesterday will still work in the next release.Loadmill’s automated-testing approach provides higher coverage compared to manual automation (i.e., substantially more lines of code go through testing), as well as much higher Velocity, meaning a reduction of the testing cycle duration from hours to minutes. 

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