everything-claude-code/rules/fsharp/testing.md

paths

paths
**/*.fs **/*.fsx **/*.fsproj

F# Testing

This file extends common/testing.md with F#-specific content.

Test Framework

• Prefer xUnit with FsUnit.xUnit for F#-friendly assertions
• Use Unquote for quotation-based assertions with clear failure messages
• Use FsCheck.xUnit for property-based testing
• Use NSubstitute or function stubs for mocking dependencies
• Use Testcontainers when integration tests need real infrastructure

Test Organization

• Mirror src/ structure under tests/
• Separate unit, integration, and end-to-end coverage clearly
• Name tests by behavior, not implementation details

open Xunit
open Swensen.Unquote

[<Fact>]
let ``PlaceOrder returns success when request is valid`` () =
    let request = { CustomerId = "cust-123"; Items = [ validItem ] }
    let result = OrderService.placeOrder request
    test <@ Result.isOk result @>

[<Fact>]
let ``PlaceOrder returns error when items are empty`` () =
    let request = { CustomerId = "cust-123"; Items = [] }
    let result = OrderService.placeOrder request
    test <@ Result.isError result @>

Property-Based Testing with FsCheck

open FsCheck.Xunit

[<Property>]
let ``order total is never negative`` (items: OrderItem list) =
    let total = Order.calculateTotal items
    total >= 0m

ASP.NET Core Integration Tests

• Use WebApplicationFactory<TEntryPoint> for API integration coverage
• Test auth, validation, and serialization through HTTP, not by bypassing middleware

Coverage

• Target 80%+ line coverage
• Focus coverage on domain logic, validation, auth, and failure paths
• Run dotnet test in CI with coverage collection enabled where available