Cucumber is an open-source tool used for software testing, specifically designed for Behavior-Driven Development (BDD). With Cucumber, testers, developers, and non-technical stakeholders can collaborate by writing tests in plain, human-readable language. This makes it easier to define and automate expectations about how the software should behave.
Cucumber allows teams to define tests in a way that both technical and non-technical team members can understand. Instead of complex code, test scenarios are written in natural language that describe how an application should behave under certain conditions.
The main goal of Cucumber is to improve communication between business, testers, and developers. Everyone can read the test scenarios and verify whether the software meets the agreed-upon requirements. Cucumber is often used in Agile development environments where fast feedback and collaboration are key.
Because of its natural language structure, Cucumber is well-suited for acceptance tests, regression tests, and automated end-to-end tests. It supports multiple programming languages such as Java, Ruby, JavaScript, and Python, making it highly versatile.
The power of Cucumber lies in its use of Gherkin. Gherkin is the language used to write test scenarios. It’s a domain-specific language that closely resembles plain English (or other supported languages), designed to capture scenarios in a clear and structured way.
With Gherkin, everyone on the project team can contribute to defining the expected functionality and test criteria. Because the syntax is simple, even team members without programming knowledge can write or review test scenarios. This helps reduce miscommunication about how the software should behave.
Gherkin is based on a few simple keywords that describe behavior. The most important ones are:
Feature: Describes the functionality being tested.
Scenario: A concrete example of behavior to be tested.
Given: The starting state.
When: The action being performed.
Then: The expected result.
And / But: Additional steps within a scenario.
Example:
Feature: Login to the website
Scenario: Successful login with valid credentials
Given the user is on the login page
When the user enters a valid email and password
And clicks the login button
Then the user is redirected to the dashboardThese scenarios are then linked to underlying code that executes the described steps.
Cucumber works by automatically linking scenarios written in plain language to test code. This makes it possible to turn behavioral descriptions directly into automated tests.
The process generally consists of four steps:
Everything starts with writing a feature file. This file contains scenarios written in Gherkin. Each feature file includes one or more scenarios that describe the desired behavior of a specific function. Since these files are written in natural language, all stakeholders can read and understand them.
The steps from the feature file are then linked to code through step definitions. These define what code should be executed when Cucumber encounters a Given, When, or Then statement.
For example:
@Given("the user is on the login page")
public void user_on_login_page() {
// Code to navigate to the login page
}A test runner is used to execute the tests. This can be done via the command line or through a test framework like JUnit (when using Java). The test runner reads the feature files, matches the scenarios to the correct step definitions, and executes the steps.
After execution, Cucumber provides clear reports showing which scenarios passed and where any failures occurred. Since the scenarios are written in plain language, the output is also easy to understand for non-technical team members.
Cucumber is closely tied to the concept of Behavior-Driven Development (BDD). This approach helps teams build software by focusing on the expected behavior before any actual code is written.
Behavior-Driven Development is a software development method where the emphasis is on describing how a system should behave in plain, understandable language. By defining expectations early, misunderstandings between business and development teams are minimized.
In BDD, different roles collaborate:
Business stakeholders describe the desired functionality.
Developers translate these descriptions into step definitions and implement the code.
Testers automate the scenarios using tools like Cucumber.
BDD promotes collaboration, communication, and continuous feedback, resulting in a shared understanding of the software being developed.
Cucumber supports the BDD process by acting as a bridge between text and code:
Business writes feature files in Gherkin.
Developers create step definitions that link the described steps to the code logic.
Testers run automated tests and provide feedback.
This creates a workflow where everyone involved understands what is being built and how it’s being tested.
Using Cucumber within a BDD approach offers several benefits:
Better communication: Everyone speaks the same language.
Fewer errors: Expectations are clearly defined upfront.
Fast feedback: Issues are discovered early.
Reusable tests: Scenarios remain useful during maintenance and future changes.
Documentation: Feature files serve as up-to-date documentation of the system.
To better understand how Cucumber works in practice, let’s walk through a full example of a simple test. In this case, we will test a scenario where a user successfully logs into a website.
First, we create the feature file. This file describes the desired behavior using Gherkin:
Feature: Login to the website
Scenario: Successful login with valid credentials
Given the user is on the login page
When the user enters a valid email and password
And clicks the login button
Then the user is redirected to the dashboardThe feature file clearly describes what should be tested, without including technical details.
Next, we link each step to code. Here’s an example using Java:
@Given("the user is on the login page")
public void user_on_login_page() {
driver.get("https://www.example.com/login");
}
@When("the user enters a valid email and password")
public void enter_valid_credentials() {
driver.findElement(By.id("email")).sendKeys("user@example.com");
driver.findElement(By.id("password")).sendKeys("securepassword");
}
@When("clicks the login button")
public void click_login_button() {
driver.findElement(By.id("loginButton")).click();
}
@Then("the user is redirected to the dashboard")
public void verify_dashboard() {
String url = driver.getCurrentUrl();
assertEquals("https://www.example.com/dashboard", url);
}In this code, a web browser (for example, through Selenium) is used to simulate the described actions.
Finally, the test is executed using a test runner, for example:
@RunWith(Cucumber.class)
@CucumberOptions(features = "src/test/resources/features")
public class TestRunner {
}The test runner automatically searches for the feature files and links each step to the correct step definitions.
While Cucumber itself is responsible for interpreting the scenarios, it requires external tools to actually execute the steps. The most common combination is Cucumber with Selenium.
Selenium is a popular tool used to automate browser actions. Combined with Cucumber, the Gherkin scenarios are linked to Selenium code. This allows full end-to-end tests to run in a real browser environment.
A typical workflow looks like this:
Cucumber reads the feature file.
The step definitions contain Selenium code.
Selenium performs the actions, such as clicking, typing, or navigating.
In this way, the behavior described in plain language is fully automated and tested inside the browser.
Besides Selenium, Cucumber can integrate with:
Appium (for mobile applications)
REST-assured (for API testing)
JUnit/TestNG (for test management in Java)
CI/CD pipelines (to automatically run tests after each code change)
This flexibility makes Cucumber suitable for web applications, mobile apps, and APIs.
Like any tool, Cucumber has its strengths and areas to be aware of.
Benefits
Readable tests: Scenarios are easy to understand for all team members.
Better collaboration: Business and IT speak the same language.
Reusable step definitions: Test steps can often be reused across scenarios.
Living documentation: Feature files act as up-to-date documentation.
Flexible integrations: Compatible with many other tools.
Limitations
Ongoing maintenance: Feature files and step definitions need to be kept up to date.
Complexity in large projects: Many scenarios can lead to longer test executions.
Technical knowledge still required: While scenarios are written in plain language, step definitions still require coding skills.
Not always ideal for all test types: For highly technical tests, other frameworks may sometimes be more efficient.
Cucumber is a powerful testing tool that helps software teams collaborate clearly and effectively on software quality. By using understandable scenarios written in Gherkin, everyone involved, from business to development, can actively participate in the testing process. Especially when combined with Behavior-Driven Development, Cucumber improves communication, reduces misunderstandings, and leads to better software quality. Thanks to its wide integration options, Cucumber is suitable for various testing environments, as long as the complexity is managed carefully.
Cucumber is used to write tests in plain language, improving collaboration between business and IT. It helps avoid misunderstandings, provides clear documentation, and enables automated testing.
Cucumber focuses on describing tests in natural language (BDD), while Selenium handles browser interactions. They’re often used together: Cucumber for scenarios, Selenium for execution.
