SpecFlow

SpecFlow is an open-source Behavior-Driven Development (BDD) framework for the .NET platform. It draws inspiration from Cucumber and enables teams to define application behavior in human-readable feature files written in the Gherkin language. Each feature contains scenarios described with Given, When, Then steps, as well as Backgrounds and Scenario Outlines with Examples.

SpecFlow links these natural-language steps to executable code by binding step definitions in C# (or VB.NET). Step definitions are methods annotated with binding attributes such as [Binding], [Given("pattern")], [When("pattern")], and [Then("pattern")], or by using regular expressions. At runtime, the test framework runs the bound methods when the corresponding Gherkin steps are encountered.

The framework integrates with .NET test ecosystems, supporting NUnit, MSTest (VSTest), and xUnit. It can be used with the SpecFlow+ Runner for enhanced features such as parallel execution and richer reporting, though standard test runners may also be employed. A typical project includes feature files alongside their corresponding step definition files, with the SpecFlow NuGet package handling code generation and execution glue.

SpecFlow also offers a Visual Studio extension to improve editing of feature files and step definitions, including syntax highlighting and IntelliSense. Additional tooling is available for living documentation and reports, such as SpecFlow Living Documentation.

Overall, SpecFlow helps translate acceptance criteria into automated tests, providing a bridge between non-technical stakeholders and developers within the .NET ecosystem.