TinyBDD — Fluent BDD for .NET, zero ceremony

Write expressive Given/When/Then tests that feel great and run anywhere (xUnit, NUnit, MSTest) without framework lock-in.

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xUnit NUnit MSTest Async-first Gherkin output

Why TinyBDD

Tiny, readable core

Understand the engine in minutes and keep it close to your tests.

Fluent, async-first

Given/When/Then chains with async built in for modern test flows.

Deferred expectations

Compose reasons and hints, throw only when awaited.

Step IO lineage

Track inputs, outputs, and the current item across steps.

Assertion agnostic

Works with any assertion library you already use.

Adapters included

Optional adapters for xUnit, NUnit, and MSTest.

Gherkin reporting

Readable Given/When/Then output right in your test results.

Try it in 30 seconds

Ambient (with adapter base class or Ambient.Current set):

```csharp await Given(() => 1) .When("double", x => x * 2) .Then("== 2", v => v == 2) .AssertPassed(); ```

Explicit (no base class required):

```csharp var ctx = Bdd.CreateContext(this); await Bdd.Given(ctx, "numbers", () => new[]{1,2,3}) .When("sum", (arr, _) => Task.FromResult(arr.Sum())) .Then("> 0", sum => sum > 0) .AssertPassed(); ```

Documentation Map

Introduction What TinyBDD is and when to use it. Getting Started Install, set up, and run your first scenario. BDD Fundamentals Core ideas and Gherkin-style thinking. BDD + TDD Workflow Practical flow from failing to passing. Writing Scenarios Crafting readable Given/When/Then steps. Data and Tables Drive tests with rich inputs and examples. Expectations Fluent assertions, reasons, and hints. Step IO and State Track state and lineage across steps. Hooks and Lifecycle Set up and tear down scenarios cleanly. Test Frameworks Adapters for xUnit, NUnit, and MSTest. Reporting Readable output for your test runs. Tips and Tricks Patterns and shortcuts for day-to-day use. Advanced Usage Extensions, customizations, and power moves. Troubleshooting Common issues and their fixes. Samples Index Working examples you can copy.

Tip: add [Feature], [Scenario], and [Tag] to make reports shine. Base classes emit Gherkin output automatically.