F# Testing Patterns
Comprehensive testing patterns for F# applications using xUnit, FsUnit, Unquote, FsCheck, and modern .NET testing practices.
When to Activate
- Writing new tests for F# code
- Reviewing test quality and coverage
- Setting up test infrastructure for F# projects
- Debugging flaky or slow tests
Test Framework Stack
| Tool | Purpose |
|---|---|
| xUnit | Test framework (standard .NET ecosystem choice) |
| FsUnit.xUnit | F#-friendly assertion syntax for xUnit |
| Unquote | Assertion library using F# quotations for clear failure messages |
| FsCheck.xUnit | Property-based testing integrated with xUnit |
| NSubstitute | Mocking .NET dependencies |
| Testcontainers | Real infrastructure in integration tests |
| WebApplicationFactory | ASP.NET Core integration tests |
Unit Tests with xUnit + FsUnit
Basic Test Structure
module OrderServiceTests
open Xunit
open FsUnit.Xunit
[<Fact>]
let ``create sets status to Pending`` () =
let order = Order.create "cust-1" [ validItem ]
order.Status |> should equal Pending
[<Fact>]
let ``confirm changes status to Confirmed`` () =
let order = Order.create "cust-1"…
