F# 中的类型bool与类型Constraints.constraint不兼容

我上过以下课程：

type numbers(Roman:string, CommonNumber:string)=
          member this.RomanNumber=Roman
          member this.ExpectedNumber=CommonNumber

          member this.MakeComparision()=
                           string (convert(Roman))= CommonNumber

然后我尝试在它上运行以下测试：

#if INTERACTIVE
#r @"..\packages\NUnit.2.6.4\lib\nunit.framework.dll"
#r @"..\packages\FsUnit.1.4.0.0\lib\net45\FsUnit.NUnit.dll"
#endif


    open NUnit.Framework
    open FsUnit


[<TestFixture>]

    type ``Given a Roman number ``()=
         let setNumbers=new numbers("XCIX","99")


         [<Test>]

         member this.
               ``Whether the right convert for this number must be exist``()=
                 setNumbers.MakeComparision() |> should be true

我不能处理它

哦，这是一个令人讨厌的问题（经常上当受骗）

您需要将

equal

与

true

值一起使用：

或者您需要将

True

约束与

be

一起使用：

member this.
       ``Whether the right convert for this number must be exist``()=
         setNumbers.MakeComparision() 
         |> should be True

见

member this.
       ``Whether the right convert for this number must be exist``()=
         setNumbers.MakeComparision() 
         |> should equal true

member this.
       ``Whether the right convert for this number must be exist``()=
         setNumbers.MakeComparision() 
         |> should be True