F# 测试模式 是做什么的？
针对 F# 应用程序的全面测试模式，使用 xUnit、FsUnit、Unquote、FsCheck 及现代 .NET 测试实践。
何时激活
- 为 F# 代码编写新测试
- 审查测试质量与覆盖率
- 为 F# 项目搭建测试基础设施
- 调试不稳定或慢速的测试
测试框架栈
| 工具 | 用途 |
|---|---|
| xUnit | 测试框架（标准 .NET 生态系统选择） |
| FsUnit.xUnit | 适用于 xUnit 的 F# 友好断言语法 |
| Unquote | 使用 F# 引用的断言库，提供清晰的失败信息 |
| FsCheck.xUnit | 与 xUnit 集成的属性基测试 |
| NSubstitute | 模拟 .NET 依赖项 |
| Testcontainers | 集成测试中的真实基础设施 |
| WebApplicationFactory | ASP.NET Core 集成测试 |
使用 xUnit + FsUnit 的单元测试
基本测试结构
module OrderServiceTests
open Xunit
open FsUnit.Xunit
[<Fact>]
let ``create 将状态设置为 Pending`` () =
let order = Order.create "cust-1" [ validItem ]
order.Status |> should equal Pending
[<Fact>]
let ``confirm 将状态改为 Confirmed`` () =
let order = Order.create "cust-1" [ validItem ]
let confirmed = Order.confirm order
confirmed.Status |> should be (ofCase <@ Confirmed @>)
使用 Unquote 进行断言
Unquote 使用 F# 引用，因此失败信息会显示完整的表达式，而不仅仅是“期望 X，得到 Y”。
module OrderValidationTests
open Xunit
open Swensen.Unquote
[<Fact>]
let ``PlaceOrder 在请求有效时返回成功`` () =
let request = { CustomerId = "cust-123"; Items = [ validItem ] }
let result = OrderService.placeOrder request
test <@ Result.isOk result @>
[<Fact>]
let ``订单总额应为各项价格之和`` () =
let items = [ { Sku = "A"; Quantity = 2; Price = 10m }
{ Sku = "B"; Quantity = 1; Price = 5m } ]
let total = Order.calculateTotal items
test <@ total = 25m @>
[<Fact>]
let ``验证过的电子邮件拒绝空输入`` () =
let result = ValidatedEmail.create ""
test <@ Result.isError result @>
异步测试
[<Fact>]
let ``PlaceOrder 在请求有效时返回成功`` () = task {
let deps = createTestDeps ()
let request = { CustomerId = "cust-123"; Items = [ validItem ] }
let! result = OrderService.placeOrder deps request
test <@ Result.isOk result @>
}
[<Fact>]
let ``PlaceOrder 在商品列表为空时返回错误`` () = task {
let deps = createTestDeps ()
let request = { CustomerId = "cust-123"; Items = [] }
let! result = OrderService.placeOrder deps request
test <@ Result.isError result @>
}
使用 Theory 的参数化测试
[<Theory>]
[<InlineData("")>]
[<InlineData(" ")>]
let ``PlaceOrder 拒绝空客户 ID`` (customerId: string) =
let request = { CustomerId = customerId; Items = [ validItem ] }
let result = OrderService.placeOrder request
result |> should be (ofCase <@ Error @>)
[<Theory>]
[<InlineData("", false)>]
[<InlineData("a", false)>]
[<InlineData("[email protected]", true)>]
[<InlineData("[email protected]", true)>]
let ``IsValidEmail 返回预期结果`` (email: string, expected: bool) =
test <@ EmailValidator.isValid email = expected @>
使用 FsCheck 进行属性基测试
使用 FsCheck.xUnit
open FsCheck
open FsCheck.Xunit
[<Property>]
let ``订单总额始终为非负数`` (items: NonEmptyList<PositiveInt * decimal>) =
let orderItems =
items.Get
|> List.map (fun (qty, price) ->
{ Sku = "SKU"; Quantity = qty.Get; Price = abs price })
let total = Order.calculateTotal orderItems
total >= 0m
[<Property>]
let ``序列化往返`` (order: Order) =
let json = JsonSerializer.Serialize order
let deserialized = JsonSerializer.Deserialize<Order> json
deserialized = order
自定义生成器
type OrderGenerators =
static member ValidEmail () =
gen {
let! user = Gen.elements [ "alice"; "bob"; "carol" ]
let! domain = Gen.elements [ "example.com"; "test.org" ]
return $"{user}@{domain}"
}
|> Arb.fromGen
[<Property(Arbitrary = [| typeof<OrderGenerators> |])>]
let ``有效的电子邮件通过验证`` (email: string) =
EmailValidator.isValid email
模拟依赖项
函数存根（推荐）
let createTestDeps () =
let mutable savedOrders = []
{ FindOrder = fun id -> task { return Map.tryFind id testData }
SaveOrder = fun order -> task { savedOrders <- order :: savedOrders }
SendNotification = fun _ -> Task.CompletedTask }
[<Fact>]
let ``PlaceOrder 保存已确认的订单`` () = task {
let mutable saved = []
let deps =
{ createTestDeps () with
SaveOrder = fun order -> task { saved <- order :: saved } }
let! _ = OrderService.placeOrder deps validRequest
test <@ saved.Length = 1 @>
}
使用 NSubstitute 模拟 .NET 接口
open NSubstitute
[<Fact>]
let ``使用正确的 ID 调用存储库`` () = task {
let repo = Substitute.For<IOrderRepository>()
repo.FindByIdAsync(Arg.Any<Guid>(), Arg.Any<CancellationToken>())
.Returns(Task.FromResult(Some testOrder))
let service = OrderService(repo)
let! _ = service.GetOrder(testOrder.Id, CancellationToken.None)
do! repo.Received(1).FindByIdAsync(testOrder.Id, Arg.Any<CancellationToken>())
}
ASP.NET Core 集成测试
type OrderApiTests (factory: WebApplicationFactory<Program>) =
interface IClassFixture<WebApplicationFactory<Program>>
let client =
factory.WithWebHostBuilder(fun builder ->
builder.ConfigureServices(fun services ->
services.RemoveAll<DbContextOptions<AppDbContext>>() |> ignore
services.AddDbContext<AppDbContext>(fun options ->
options.UseInMemoryDatabase("TestDb") |> ignore) |> ignore))
.CreateClient()
[<Fact>]
member _.``GET order 在未找到时返回 404`` () = task {
let! response = client.GetAsync($"/api/orders/{Guid.NewGuid()}")
test <@ response.StatusCode = HttpStatusCode.NotFound @>
}
测试组织结构
tests/
MyApp.Tests/
Unit/
OrderServiceTests.fs
PaymentServiceTests.fs
Integration/
OrderApiTests.fs
OrderRepositoryTests.fs
Properties/
OrderPropertyTests.fs
Helpers/
TestData.fs
TestDeps.fs
常见反模式
| 反模式 | 修复方案 |
|---|---|
| 测试实现细节 | 测试行为和结果 |
| 可变共享测试状态 | 每个测试使用全新状态 |
异步测试中使用 Thread.Sleep | 使用 Task.Delay 并设置超时，或使用轮询辅助方法 |
对 sprintf 输出进行断言 | 对类型化值和模式匹配进行断言 |
忽略 CancellationToken | 始终传递并验证取消 |
| 跳过属性基测试 | 对任何具有明确不变量的函数使用 FsCheck |
相关技能
dotnet-patterns- 惯用 .NET 模式、依赖注入和架构csharp-testing- C# 测试模式（共享基础设施如 WebApplicationFactory 和 Testcontainers 同样适用于 F#）
运行测试
# 运行所有测试
dotnet test
# 运行并收集覆盖率
dotnet test --collect:"XPlat Code Coverage"
# 运行指定项目
dotnet test tests/MyApp.Tests/
# 按测试名称筛选
dotnet test --filter "FullyQualifiedName~OrderService"
# 开发期间使用监视模式
dotnet watch test --project tests/MyApp.Tests/