public void ExistsReturnsBool()
{
//Arrange
var moq = new Mock <IDocumentsRepository>();
moq.Setup(m => m.Exists(It.IsAny <int>(), It.IsAny <string>())).Returns(Task.FromResult(true));
DocumentsController controller = new DocumentsController(moq.Object);
//Act
var result = controller.Exists(0, string.Empty).Result;
//Assert
Assert.IsInstanceOfType(result, typeof(bool));
Assert.IsTrue(result);
}