Reqnroll Feature File Tutorial: BDD Syntax (Given When Then)

This article is part of the “Introduction to E2E Testing with Reqnroll × Playwright” series.

• Reqnroll + Playwright E2E Testing Guide for C# (.NET) — Beginner to Practical Setup

Reqnroll Feature File Tutorial: BDD Syntax (Given When Then)

Conclusion

Reqnroll Feature files let you write test scenarios in plain, human-readable language using BDD.
By using Given / When / Then, you can create tests that are easy to understand, maintain, and share across teams.

What You’ll Learn in This Guide

In this tutorial, you’ll learn:

• What a Feature file is
• How Given / When / Then work
• Basic Gherkin syntax in Reqnroll
• Real examples of Feature files
• Best practices for writing clean scenarios

This guide is perfect for developers getting started with BDD in .NET using Reqnroll.

What Is a Feature File?

A Feature file is a text file where you describe test scenarios in a readable format.

File Extension

.feature

Example

Login.feature

Feature files use Gherkin syntax, which allows you to describe behavior like a specification.

Basic Structure of a Feature File

A typical Feature file looks like this:

Feature: Login

Scenario: Successful login
  Given I open the login page
  When I enter valid credentials
  Then I should see the dashboard

This structure describes user actions and expected results.

BDD Keywords Explained

Feature files rely on a small set of keywords:

Keyword	Meaning
Feature	The functionality being tested
Scenario	A single test case
Given	Preconditions
When	User actions
Then	Expected results
And	Additional steps

These keywords form the foundation of BDD-style testing.

Example: Login Scenario

Here’s a more complete example:

Feature: Login

Scenario: Login with valid credentials
  Given I open the login page
  When I enter email "test@example.com"
  And I enter password "password123"
  And I click the login button
  Then I should see the dashboard

What This Scenario Does

• Opens the login page
• Enters email and password
• Clicks the login button
• Verifies the dashboard is displayed

This mirrors real user behavior in a clear and readable way.

How to Write Each Section

Feature

The Feature describes what functionality you are testing.

Feature: Login

You can also add a description:

Feature: User Login
  Verify that users can log into the application

Scenario

A Scenario represents a single test case.

Scenario: Login with valid credentials

You can define multiple scenarios under one feature:

• Successful login
• Invalid password
• Empty input

Given

Given defines the initial state or precondition.

Given I open the login page

When

When describes user actions.

When I enter email "test@example.com"
And I enter password "password123"

Use And to chain multiple actions.

Then

Then defines the expected result.

Then I should see the dashboard

This step verifies that the test passed.

Using Parameters in Feature Files

You can pass dynamic values using parameters:

When I enter email "test@example.com"

These values are passed to Step Definitions.

Example (C# Step Definition)

[When(@"I enter email ""(.*)""")]
public async Task EnterEmail(string email)
{
    await _page.Locator("#email").FillAsync(email);
}

This connects your Feature file to executable test code.

Best Practices for Writing Feature Files

Write from the User’s Perspective

Focus on user behavior, not technical details.

• ❌ Click button #login
• ✅ Click the login button

Avoid Implementation Details

Feature files should describe what, not how.

• ❌ Use CSS selector #login
• ✅ Click the login button

Keep Scenarios Short

Each Scenario should have a single purpose.

• One for success
• One for failure

This keeps tests clear and maintainable.

How Reqnroll Executes Feature Files

Reqnroll runs tests using the following flow:

Feature File
     ↓
Step Definitions (C#)
     ↓
Test Code (Playwright, etc.)

The steps in your Feature file are matched with C# methods, which execute the actual test logic.

Summary

Reqnroll Feature files are the foundation of BDD testing in .NET.

Key takeaways:

• Feature files use Gherkin syntax
• Core structure: Feature, Scenario, Given, When, Then
• Tests are written in a human-readable format
• Scenarios should be simple and user-focused
• Feature files connect directly to C# test code

By mastering Feature files, you can create clear, maintainable, and scalable BDD test scenarios.