private IRepository<Country> CreateMockRepository()
        {
            Mock<IRepository<Country>> mock = new Mock<IRepository<Country>>();
            mock.Setup(m => m.Table).Returns(new Country[]
            {
                new Country {ID =1, Name ="Country1" },
                new Country {ID =2, Name ="Country2" }
            }.AsQueryable());

            return mock.Object;
        }

[TestMethod]
    public void Insert_Country()
    {
        //Arrange - create mock repository               
        var moq = CreateMockRepository();

        //Arrange - create a controller

        var config = new HttpConfiguration();
        var request = new HttpRequestMessage(HttpMethod.Post, "http://localhost/api/country");
        var route = config.Routes.MapHttpRoute("DefaultApi", "api/{controller}");
        var routeData = new HttpRouteData(route, new HttpRouteValueDictionary { { "controller", "country" } });
        CountryController target = new CountryController(moq);
        target.ControllerContext = new HttpControllerContext(config, routeData, request);
        target.Request = request;
        target.Request.Properties[HttpPropertyKeys.HttpConfigurationKey] = config;

        Country newCountry = new Country(){ ID = 10, Name = "TEST" };

        //Action
        var result = target.Post(newCountry);
        var result2 = target.Get().ToArray();

        //Assert 1
        Assert.AreEqual(HttpStatusCode.Created, result.StatusCode);            

        //Assert 2
        Assert.AreEqual(3, result2.Length);
    }

private IRepository<Country> CreateMockRepository()
{
    var countries = new List<Country> {
        new Country { ID=1, Name="Country1" },
        new Country { ID=2, Name="Country2" }
    };

    Mock<IRepository<Country>> mock = new Mock<IRepository<Country>>();

    mock.Setup(m => m.Table).Returns(countries.AsQueryable());

    mock.Setup(m => m.Insert(It.IsAny<Country>()))
        .Callback<Country>(c => countries.Add(c));

    return mock.Object;
}