public void CreateAssignmentTest()
        {
            var options = new DbContextOptionsBuilder <AppDBContext>()
                          .UseInMemoryDatabase(databaseName: "AssignmentCreateDatabase")
                          .Options;

            using (var context = new AppDBContext(options))
            {
                context.Assignment.Add(new Assignment {
                    Id = "1", Name = "1", Description = "1"
                });
                context.Assignment.Add(new Assignment {
                    Id = "2", Name = "2", Description = "2"
                });
                context.Assignment.Add(new Assignment {
                    Id = "3", Name = "3", Description = "3"
                });
                context.SaveChanges();
            }

            using (var context = new AppDBContext(options))
            {
                AssignmentRepository assignmentRepository = new AssignmentRepository(context);
                assignmentRepository.Create(new Assignment {
                    Id = "4", Name = "4", Description = "4"
                });
                context.SaveChanges();
                List <Assignment> assignments = assignmentRepository.GetAll().ToList();
                Assert.Equal(4, assignments.Count);
            }
        }