A.CallTo(...).ReturnsLazily(...)抛出"指定的对象不被识别为伪对象."

Question

在C#我曾经写过

var provider = A.Fake<ITimeProvider>();
A.CallTo(() => provider.Fetch()).ReturnsLazily(call => data[0]);
container.Register(() => provider);

捕获呼叫Fetch().

当我尝试用F#做同样的事情时

let provider = A.Fake<ITimeProvider>()
A.CallTo(fun () -> provider.Fetch()).ReturnsLazily(fun call -> data.[0]) |> ignore
container.Register(fun () -> provider)

测试失败了

Test Error : ....Test
System.ArgumentException : The specified object is not recognized as a fake object.
at Microsoft.FSharp.Control.AsyncBuilderImpl.commit[a](Result`1 res)
at Microsoft.FSharp.Control.CancellationTokenOps.RunSynchronously[a](CancellationToken token, FSharpAsync`1 computation, FSharpOption`1 timeout)
at Microsoft.FSharp.Control.FSharpAsync.RunSynchronously[T](FSharpAsync`1 computation, FSharpOption`1 timeout, FSharpOption`1 cancellationToken)
...

对于F#来说,它的定义应该有点不同.你知道怎么样？

Answer 1

FakeItEasy使用F#3支持的LINQ表达式,但是在使用静态API时似乎存在不兼容性.基于错误消息"对象未被识别为伪对象"我怀疑在这种情况下,对象的分辨率是C#/ VB.Net特定的.

然而,FakeItEasy基于实例成员的设置似乎有效:

let fake = Fake<ITimeProvider>()
fake.CallsTo(fun x -> x.Fetch()).ReturnsLazily(fun () -> data.[0]) |> ignore
let provider = fake.FakedObject

另一种选择是使用F#和Moq(这里我使用的是Moq.FSharp.Extensions):

let mock = Mock<ITimeProvider>()
mock.SetupFunc(fun x -> x.Fetch()).Returns(data.[0]).End
let provider = mock.Object

或者Foq,专为F#设计:

let provider = 
    Mock<ITimerProvider>.Method(fun x -> <@ x.Fetch @>).Returns(data.[0])