How can I mock HttpRequestMessage, specifically the CreateResponse?

How can I mock HttpRequestMessage, specifically the CreateResponse?

var requestMessage = Substitute.For<HttpRequestMessage>();
requestMessage.CreateResponse().ReturnsForAnyArgs(
       new HttpResponseMessage(HttpStatusCode.OK));

but I get the exception ...

NSubstitute.Exceptions.CouldNotSetReturnDueToNoLastCallException: 
  'Could not find a call to return from.

I've seen the questions ... How to mock the CreateResponse<T> extension method on HttpRequestMessage

And associated ... ASP.NET WebApi unit testing with Request.CreateResponse ...

But they don't seem to actually end up mocking the CreateResponse

Additional comments:

I'm trying to write a unit test around the starter of an Azure precompiled C# function ...

[FunctionName("Version")]
public static HttpResponseMessage Run(
    [HttpTrigger(AuthorizationLevel.Anonymous, "get", "post", Route = null)]
    HttpRequestMessage req,
    TraceWriter log)
{
    log.Info("Version function processed a request ... ");

    return req.CreateResponse(HttpStatusCode.OK, "Version 0.0.1");
}

and the actual test, where I want to mock up the HttpRequestMessage, specifically the CreateReponse where I get the error is ...

[TestMethod]
public void Version_returns_value()
{
    var requestMessage = Substitute.For<HttpRequestMessage>();
    requestMessage.CreateResponse(Arg.Any<HttpStatusCode>(), Arg.Any<string>())
                  .Returns(new HttpResponseMessage(HttpStatusCode.OK));
    var log = new CustomTraceWriter(TraceLevel.Verbose);

    var httpResponseMessage = VersionFunction.Run(requestMessage, log);
    var httpContent = httpResponseMessage.Content;

    httpContent.Should().Be("Version 0.0.1 :: valid");
}