public void ReturnsNullIfKeyIsInvalid()
 {
     using (var dbContext = new TestDbContextContainer())
     {
         using (var repository = new DbContextCustomerRepository(dbContext))
         {
             Assert.IsNull(repository.GetByKey(12345));
         }
     }
 }

 public void ThrowsArgumentNullExceptionForNullExpression()
 {
     using (var dbContext = new TestDbContextContainer())
     {
         using (var repository = new DbContextCustomerRepository(dbContext))
         {
             ExceptionTester.CallMethodAndExpectException<ArgumentNullException>(() => repository.GetAll().Include(null));
         }
     }
 }

 public void ThrowsExceptionWhenTableDoesNotContainEntity()
 {
     using (var dbContext = new TestDbContextContainer())
     {
         using (var repository = new DbContextCustomerRepository(dbContext))
         {
             ExceptionTester.CallMethodAndExpectException<InvalidOperationException>(() => repository.Single(x => x.Id == 999));
         }
     }
 }

            public void IncludesEntitiesUsingExpression()
            {
                using (var dbContext = new TestDbContextContainer())
                {
                    using (var repository = new DbContextCustomerRepository(dbContext))
                    {
                        EFTestHelper.CreateCustomerIfNotAlreadyExists(42);

                        var existingCustomer = repository.GetAll().Include(x => x.DbContextOrders).FirstOrDefault();

                        Assert.IsNotNull(existingCustomer);
                    }
                }
            }

            public void ReturnsEntityIfKeyIsValid()
            {
                using (var dbContext = new TestDbContextContainer())
                {
                    using (var repository = new DbContextCustomerRepository(dbContext))
                    {
                        EFTestHelper.CreateCustomerIfNotAlreadyExists(42);

                        var existingCustomer = repository.GetByKey(42);

                        Assert.IsNotNull(existingCustomer);
                    }
                }
            }

            public void ReturnsEntityWhenTableContainsEntity()
            {
                using (var dbContext = new TestDbContextContainer())
                {
                    using (var repository = new DbContextCustomerRepository(dbContext))
                    {
                        EFTestHelper.CreateCustomerIfNotAlreadyExists(1);

                        var customer = repository.Single(x => x.Id == 1);

                        Assert.IsNotNull(customer);
                        Assert.AreEqual(1, customer.Id);
                    }
                }
            }

        public static void CreateCustomerIfNotAlreadyExists(int id)
        {
            using (var dbContext = new TestDbContextContainer())
            {
                using (var repository = new DbContextCustomerRepository(dbContext))
                {
                    var existingCustomer = repository.FirstOrDefault(x => x.Id == id);
                    if (existingCustomer == null)
                    {
                        var customer = CreateCustomer(id);

                        repository.Add(customer);

                        dbContext.SaveChanges();
                    }
                }
            }
        }

 public void ReturnsNullWhenTableContainsEntity()
 {
     using (var dbContext = new TestDbContextContainer())
     {
         using (var repository = new DbContextCustomerRepository(dbContext))
         {
             var customer = repository.SingleOrDefault(x => x.Id == 999);
             Assert.IsNull(customer);
         }
     }
 }

            public void ReturnsCorrectEntityCount()
            {
                using (var dbContext = new TestDbContextContainer())
                {
                    using (var repository = new DbContextCustomerRepository(dbContext))
                    {
                        EFTestHelper.CreateCustomerIfNotAlreadyExists(100);
                        EFTestHelper.CreateCustomerIfNotAlreadyExists(101);
                        EFTestHelper.CreateCustomerIfNotAlreadyExists(102);

                        var customerCount = repository.Count(x => x.Id >= 100 && x.Id <= 102);

                        Assert.AreEqual(3, customerCount);
                    }
                }
            }

            public void ReturnsCorrectEntities()
            {
                using (var dbContext = new TestDbContextContainer())
                {
                    using (var repository = new DbContextCustomerRepository(dbContext))
                    {
                        EFTestHelper.CreateCustomerIfNotAlreadyExists(100);
                        EFTestHelper.CreateCustomerIfNotAlreadyExists(101);
                        EFTestHelper.CreateCustomerIfNotAlreadyExists(102);

                        var customers = repository.GetAll().ToList();

                        Assert.IsTrue(customers.Count >= 3);
                    }
                }
            }

            public void UpdatesEntity()
            {
                using (var dbContext = new TestDbContextContainer())
                {
                    using (var repository = new DbContextCustomerRepository(dbContext))
                    {
                        EFTestHelper.CreateCustomerIfNotAlreadyExists(301);

                        var customer1 = repository.GetByKey(301);
                        customer1.Name = "John Doe";

                        repository.Update(customer1);

                        dbContext.SaveChanges();

                        var customer2 = repository.GetByKey(301);

                        Assert.IsNotNull(customer2);
                        Assert.AreEqual("John Doe", customer2.Name);
                    }
                }
            }

            public void SucceedsWhenEntitiesMatchFilter()
            {
                using (var dbContext = new TestDbContextContainer())
                {
                    using (var repository = new DbContextCustomerRepository(dbContext))
                    {
                        EFTestHelper.CreateCustomerIfNotAlreadyExists(201);
                        EFTestHelper.CreateCustomerIfNotAlreadyExists(202);
                        EFTestHelper.CreateCustomerIfNotAlreadyExists(203);

                        repository.Delete(x => x.Id >= 201 && x.Id <= 203);

                        dbContext.SaveChanges();

                        Assert.IsNull(repository.GetByKey(201));
                        Assert.IsNull(repository.GetByKey(202));
                        Assert.IsNull(repository.GetByKey(203));
                    }
                }
            }

            public void SucceedsWhenNoEntitiesMatchFilter()
            {
                using (var dbContext = new TestDbContextContainer())
                {
                    using (var repository = new DbContextCustomerRepository(dbContext))
                    {
                        repository.Delete(x => x.Id == 999);

                        dbContext.SaveChanges();
                    }
                }
            }

            public void DeletesSpecificEntity()
            {
                using (var dbContext = new TestDbContextContainer())
                {
                    using (var repository = new DbContextCustomerRepository(dbContext))
                    {
                        EFTestHelper.CreateCustomerIfNotAlreadyExists(201);

                        var customer1 = repository.GetByKey(201);

                        Assert.IsNotNull(customer1);

                        repository.Delete(customer1);

                        dbContext.SaveChanges();

                        var customer2 = repository.GetByKey(201);

                        Assert.IsNull(customer2);
                    }
                }
            }

 public void ThrowsArgumentNullExceptionForNullEntity()
 {
     using (var dbContext = new TestDbContextContainer())
     {
         using (var repository = new DbContextCustomerRepository(dbContext))
         {
             ExceptionTester.CallMethodAndExpectException<ArgumentNullException>(() => repository.Delete((DbContextCustomer)null));
         }
     }
 }

            public void AddsNonExistingEntity()
            {
                using (var dbContext = new TestDbContextContainer())
                {
                    using (var repository = new DbContextCustomerRepository(dbContext))
                    {
                        var customer = EFTestHelper.CreateCustomer(1235);

                        repository.Attach(customer);

                        dbContext.SaveChanges();

                        var fetchedCustomer = repository.GetByKey(1235);
                        Assert.AreEqual(customer, fetchedCustomer);
                    }
                }
            }