public async Task GetClients_ShouldIncludeCategoriesWithClients_WhenCategoriesAssigned()
        {
            // Arrange
            using (var context = new AppDbContext(_dbContextOptions))
            {
                context.Clients.Add(new Client {
                    Category = new Category {
                        Name = "a"
                    }
                });
                context.Clients.Add(new Client {
                    Category = new Category {
                        Name = "b"
                    }
                });
                await context.SaveChangesAsync();
            }

            // Act
            using (var context = new AppDbContext(_dbContextOptions))
            {
                var service = new ClientsDataService(context);
                var result  = await service.GetClients();

                // Assert
                result.First().Category.Name.Should().Be("a");
                result.Last().Category.Name.Should().Be("b");
            }
        }
        public async Task GetClients_ShouldReturnTwoClients_WhenTwoClientsFoundInDatabase()
        {
            // Arrange
            using (var context = new AppDbContext(_dbContextOptions))
            {
                context.Clients.AddRange(new Client(), new Client());
                await context.SaveChangesAsync();
            }

            // Act
            using (var context = new AppDbContext(_dbContextOptions))
            {
                var service = new ClientsDataService(context);
                var result  = await service.GetClients();

                // Assert
                result.Should().HaveCount(2);
            }
        }