public void GetOfferByIdTest()
{
int id = 1;
IHttpActionResult result = _controller.Get(id);
var contentResult = result as OkNegotiatedContentResult <Offer>;
Offer o = _context.Offers.FirstOrDefault(of => of.Id == id);
Assert.IsNotNull(o);
Assert.IsNotNull(contentResult);
Assert.IsNotNull(contentResult.Content);
Assert.AreEqual(o.VendorId, contentResult.Content.VendorId);
}