c# - 如何最小化 Entity Framework SaveChangesAsync？

Question

Mock<IDbContext> dbContext;

[TestFixtureSetUp]
public void SetupDbContext()
{
    dbContext = new Mock<IDbContext>();
    dbContext.Setup(c => c.SaveChanges()).Verifiable();
    dbContext.Setup(c => c.SaveChangesAsync()).Verifiable();
    dbContext.Setup(c => c.Customers.Add(It.IsAny<Customer>()))
             .Returns(It.IsAny<Customer>()).Verifiable();
}

[Test]
public async Task AddCustomerAsync()
{
    //Arrange
    var repository = new EntityFrameworkRepository(dbContext.Object);
    var customer = new Customer() { FirstName = "Larry", LastName = "Hughes" };

    //Act
    await repository.AddCustomerAsync(customer);

    //Assert
    dbContext.Verify(c => c.Customers.Add(It.IsAny<Customer>()));
    dbContext.Verify(c => c.SaveChangesAsync());
}

[Test]
public void AddCustomer()
{
    //Arrange
    var repository = new EntityFrameworkRepository(dbContext.Object);
    var customer = new Customer() { FirstName = "Larry", LastName = "Hughes" };

    //Act
    repository.AddCustomer(customer);

    //Assert
    dbContext.Verify(c => c.Customers.Add(It.IsAny<Customer>()));
    dbContext.Verify(c => c.SaveChanges());
}

这是我要测试的内容:

public class EntityFrameworkRepository
{
    private readonly IDbContext DBContext;

    public EntityFrameworkRepository(IDbContext context)
    {
        DBContext = context;
    }

    public async Task AddCustomerAsync(Customer customer)
    {
        DBContext.Customers.Add(customer);
        await DBContext.SaveChangesAsync();
    }

    public void AddCustomer(Customer customer)
    {
        DBContext.Customers.Add(customer);
        DBContext.SaveChanges();
    }
}

AddCustomers 测试通过。

AddCustomersAsync 测试失败，我在调用 await DbContext.SaveChangesAsync() 后不断收到 NullReferenceException。

at MasonOgCRM.DataAccess.EF.EntityFrameworkRepository.d__2.MoveNext() in C:\Users\Mason\Desktop\Repositories\masonogcrm\src\DataAccess.EFRepository\EntityFrameworkRepository.cs:line 43

我在代码中看不到任何 null。 DbContext 不为空。 AddCustomers 的等效测试与预期相同，只是不是异步运行。我怀疑我没有在 SetupDBContext() 中执行正确的 SaveChangesAsync 设置，但我不知道如何修复它。

Answer 1

你是对的，问题的发生是因为你的设置不正确::dbContext.Setup(c => c.SaveChangesAsync()).Verifiable();.

该方法返回一个 Task，而您忘记返回一个 Task，因此返回 null。

您可以删除 dbContext.Setup(c => c.SaveChangesAsync()).Verifiable(); 或 将设置更改为:

dbContext.Setup(c => c.SaveChangesAsync()).Returns(() => Task.Run(() =>{})).Verifiable();