.net 模拟和单元测试需要时如何抛出 SqlException

由于您使用的是LINQtoSQL，下面是一个使用NUnit和Moq测试您提到的场景的示例.我不知道你的DataContext的确切细节，也不知道你可以从中获得什么.根据你的需要编辑.

您需要用自定义类包装DataContext，不能用Moq模拟DataContext.您也不能模拟SqlException，因为它是密封的.您需要用自己的异常类来包装它.完成这两件事并不难.

让我们从创建测试开始:

[Test]
public void FindBy_When_something_goes_wrong_Should_handle_the_CustomSqlException()
{
    var mockDataContextWrapper = new Mock<IDataContextWrapper>();
    mockDataContextWrapper.Setup(x => x.Table<User>()).Throws<CustomSqlException>();

    IUserResository userRespoistory = new UserRepository(mockDataContextWrapper.Object);
    // Now, because we have mocked everything and we are using dependency injection.
    // When FindBy is called, instead of getting a user, we will get a CustomSqlException
    // Now, inside of FindBy, wrap the call to the DataContextWrapper inside a try catch
    // and handle the exception, then test that you handled it, like mocking a logger, then passing it into the repository and verifying that logMessage was called
    User user = userRepository.FindBy(1);
}

让我们实现测试，首先让我们使用存储库模式包装Linq到Sql调用:

public interface IUserRepository
{
    User FindBy(int id);
}

public class UserRepository : IUserRepository
{
    public IDataContextWrapper DataContextWrapper { get; protected set; }

    public UserRepository(IDataContextWrapper dataContextWrapper)
    {
        DataContextWrapper = dataContextWrapper;
    }

    public User FindBy(int id)
    {
        return DataContextWrapper.Table<User>().SingleOrDefault(u => u.UserID == id);
    }
}

接下来像这样创建IDataContextWrapper，你可以查看这个主题的blog post，我的有点不同:

public interface IDataContextWrapper : IDisposable
{
    Table<T> Table<T>() where T : class;
}

接下来创建CustomSqlException类:

public class CustomSqlException : Exception
{
 public CustomSqlException()
 {
 }

 public CustomSqlException(string message, SqlException innerException) : base(message, innerException)
 {
 }
}

以下是IDataContextWrapper的示例实现:

public class DataContextWrapper<T> : IDataContextWrapper where T : DataContext, new()
{
 private readonly T _db;

 public DataContextWrapper()
 {
        var t = typeof(T);
     _db = (T)Activator.CreateInstance(t);
 }

 public DataContextWrapper(string connectionString)
 {
     var t = typeof(T);
     _db = (T)Activator.CreateInstance(t, connectionString);
 }

 public Table<TableName> Table<TableName>() where TableName : class
 {
        try
        {
            return (Table<TableName>) _db.GetTable(typeof (TableName));
        }
        catch (SqlException exception)
        {
            // Wrap the SqlException with our custom one
            throw new CustomSqlException("Ooops...", exception);
        }
 }

 // IDispoable Members
}