public void PostReturnsDocument()
{
//Arrange
var moq = new Mock <IDocumentsRepository>();
moq.Setup(m => m.Post(It.IsAny <Document>())).Returns <Document>(d => Task.FromResult(d));
DocumentsController controller = new DocumentsController(moq.Object);
//Act
var result = (controller.Post(new Document()).Result as OkObjectResult).Value;
//Assert
Assert.IsInstanceOfType(result, typeof(Document));
}