Record with List of Records Unit Test Failing - unit-testing

Question

I have the following records:
namespace FunctionalInnovate.Domain
module Voting=
open System
type Vote = {
VoteId : int
SuggestionId : int
VotePreference : int
}
type Suggestion = {
SuggetionId : int
SuggestionText : string
}
type User = {
UserId : int
Votes : Vote list
}
From these records, I have created the following Unit Test:
module ``Voting Tests``
open NUnit.Framework
open FsUnit
open FunctionalInnovate.Domain.Voting
[<Test>]
let``Get Vote from given SuggestionId``()=
let votePreference = 1
let vote1 = { VoteId = 1; SuggestionId = 34; VotePreference = votePreference }
let vote2 = { VoteId = 2; SuggestionId = 654; VotePreference = votePreference}
let votes = [ vote1; vote2; ]
let user = {UserId = 321; Votes = votes}
Assert.IsTrue(true) |> ignore
I've just changed the Assert statement to something simple at this point as it keeps failing at present. Using ReSharper, when I run the test I get an error. Upon investigation, it appears to be a problem with the List of Votes being assigned to the Votes type within my user declaration. What I find strange though is that if I load all of the types into FSI and then load each line of the test in turn, it works without any errors.
Anyone got any ideas as to why the unit test is failing?
The error ReSharper Test Runner is producing is:
System.MissingMethodException : Method not found: 'Void User..ctor(Int32, Microsoft.FSharp.Collections.FSharpList`1<Vote>)'.
at Voting Tests.Get Vote from given SuggestionId()

Answer 1

As per #Tomas Petricek and #John Palmer's advice, it was an issue with my ''FSharp.Core.dll'' version.
The version of this DLL in my UnitTest project was much older than what was in my Domain project.
All I did to fix it was going into NuGet Package Manager and update that specific package. Upon running my tests again, everything was green and healthy.