C#+模拟服务层？

Question

我刚刚开始使用Moq进行单元测试/模拟,并遇到了问题..

我有一个名为"CustomerService"的服务层,它有以下代码:

public interface ICustomerService
{
    Customer GetCustomerById(int id);
}

public class CustomerService : ICustomerService
{
    private IRepository<Customer> customerRepository;

    public CustomerService(IRepository<Customer> rep)
    {
        customerRepository = rep;
    }
    public Customer GetCustomerById(int id)
    {
        var customer = customerRepository.Get(x => x.CustomerId == id);

        if (customer == null)
            return null;

        return customer;
    }
}

我的存储库类是通用的,并且遵循:

public interface IRepository<T> : IDisposable where T : class
    {
        T Get(Expression<Func<T, bool>> predicate);
    }

    public class Repository<T> : IRepository<T> where T : class
    {
        private ObjectContext context;
        private IObjectSet<T> objectSet;

        public Repository()
            : this(new demonEntities())
        {
        }

        public Repository(ObjectContext ctx)
        {
            context = ctx;
            objectSet = context.CreateObjectSet<T>();
        }

        public T Get(Expression<Func<T, bool>> predicate)
        {
            T entity = objectSet.Where<T>(predicate).FirstOrDefault();

            if (entity == null)
                return null;

            return objectSet.Where<T>(predicate).FirstOrDefault();
        }

        public void Dispose()
        {
            Dispose(true);
            GC.SuppressFinalize(this);
        }

        protected virtual void Dispose(bool disposing)
        {
            if (disposing)
            {
                if (context != null)
                {
                    context.Dispose();
                    context = null;
                }
            }
        }
    }

现在是我的问题..如何进行单元测试以检查我的GetCustomerById是否返回null？

已经尝试过:

[TestMethod]
public void GetCustomerTest()
{
    const int customerId = 5;

    var mock = new Mock<IRepository<Customer>>();
    mock.Setup(x => x.Get(z => z.CustomerId == customerId))
        .Returns(new Customer());

    var repository = mock.Object;
    var service = new CustomerService(repository);
    var result = service.GetCustomerById(customerId);

    Assert.IsNotNull(result);
}

没有运气......

Answer 1

您需要将Repository<T>.Get方法设置为虚拟,以便Moq可以覆盖它并返回您设置的值:

public virtual T Get(Expression<Func<T, bool>> predicate)

在你的测试中,改变

mock.Setup(x => x.Get(z => z.CustomerId == customerId))
        .Returns(new Customer());

至

mock.Setup(x => x.Get(It.IsAny<Expression<Func<Customer, bool>>>()))
        .Returns(new Customer());

它表示返回Customer任何Expression<Func<Customer, bool>>传入的新内容.理想情况下,您将测试一个特定的表达式,但根据这个SO问题的接受答案,Moq不能这样做.

如果您想测试您的服务层没有Customer对存储库返回的任何意外做任何事情,而不是测试以查看是否有任何 Customer返回,您可以设置模拟Customer(确保使CustomerId属性为虚拟)并断言Customer由服务层返回的具有预期的属性.

[TestMethod]
public void GetCustomerTest()
{
    const int customerId = 5;

    var mockCustomer = new Mock<Customer>();

    mockCustomer.SetupGet(x => x.CustomerId)
        .Returns(customerId);

    var mock = new Mock<IRepository<Customer>>();

    mock.Setup(x => x.Get(It.IsAny<Expression<Func<Customer, bool>>>()))
        .Returns(mockCustomer.Object);

    var repository = mock.Object;
    var service = new CustomerService(repository);
    var result = service.GetCustomerById(customerId);

    Assert.AreEqual(customerId, result.CustomerId);
}

HTH