How do I unit test a Windows Azure Table query with a stub using Moq?

Question

I cannot get my unit test to work correctly. It works in the integration test that I have, where it really gets into the Azure table storage. The problem, I think, is a mockery of the QueryableEntities property , which retrieves the Queryable from mock but returns a DataServiceQuery from the ServiceContext class. Is it possible to create a stub of type DataServiceQuery that returns a Queryable?

This is my code:

Test

[TestMethod]
    public void GetAExistingWordInStorageShouldReturnCorrectWord()
    {

        Word expected = new Word(Dictionaries.Swedish.ToString(), "Word", "Word");

        List<Word> Words = new List<Word>();
        Words.Add(new Word(Dictionaries.Swedish.ToString(), "Word", "Word"));

        IQueryable<Word> WordQueryable = Words.AsQueryable<Word>();

        var mock = new Mock<IServiceContext<Word>>();
        mock.Setup(x => x.QueryableEntities).Returns(WordQueryable);

        DictionaryRepository dr = new DictionaryRepository(Models.Dictionaries.Swedish, "testdictionaries");
        dr.Context = mock.Object;

        Word result = dr.GetWord(expected.Text, false);

        Assert.AreEqual(expected, result);
    }

Interface IServiceContect

public interface IServiceContext<TEntity>
{
    IQueryable<TEntity> QueryableEntities {get;}
}

Class ServiceContext

public class ServiceContext<TEntity> : TableServiceContext, IServiceContext<TEntity> where TEntity : TableServiceEntity
{

    private readonly string tableName;

    public ServiceContext(CloudStorageAccount account, String tableName)
        : base(account.TableEndpoint.ToString(), account.Credentials)
    {
        this.tableName = tableName;
        this.IgnoreResourceNotFoundException = true;
    }

    public IQueryable<TEntity> QueryableEntities
    {
        get
        {
            return CreateQuery<TEntity>(tableName);
        }
    }

}

Dictionary repository

     public class DictionaryRepository : IDictionaryRepository
{
    public Dictionaries Dictionary { get; set; }
    public String TableName;

    public IServiceContext<Word> Context;

    public DictionaryRepository(Dictionaries dictionary)
        : this(dictionary, "dictionaries")
    {
    }

    public DictionaryRepository(Dictionaries dictionary, String tableName)
    {
        Dictionary = dictionary;
        this.TableName = tableName;
        CloudStorageAccount account = CloudStorageAccount.Parse(***);
        Context = new ServiceContext<Word>(account, this.TableName);
    }

    public List<Tile> GetValidTiles()
    {
        throw new NotImplementedException();
    }

    public Type ResolveEntityType(String name)
    {
        return typeof(Word);
    }

    public Word GetWord(string word, Boolean useCache = false)
    {

        var q = this.Context.QueryableEntities.Where(x => x.PartitionKey == Dictionary.ToString() && x.RowKey == word).AsTableServiceQuery();

        Word result = q.Execute().SingleOrDefault();

        if (result == null)
            return null;

        return result;

    }} 

I get the following error

Error:

    ArgumentNullException was unhandeled by user code
    Value cannot be null.
    Parameter name: query

.AsTableServiceQuery() DictionaryRepository:

var q = this.Context.QueryableEntities.Where(x => x.PartitionKey == Dictionary.ToString() && x.RowKey == word).AsTableServiceQuery();

Answer 1

, , QueryableEntities readonly, mock.SetupGet mock.Setup.

EDIT:

, , .AsTableServiceQuery() IQueryable<T> DataServiceQuery<T>, .

, , . Windows Azure Storage: TDD mocks

Answer 2

, , , Moq, , , - Fakes.

http://azurator.blogspot.com/2013/07/unit-testing-azure-table-storage-queries.html

Shim CloudTableQuery<T>, Expression, , IEnumerable, :

[TestMethod]
public void here_is_my_test()
{
    IEnumerable<MyEntityType> fakeResults = GetFakeResults();

    using (ShimsContext.Create())
    {
        InterceptCloudTableQueryExecute<MyEntityType>(fakeResults);

        DoQuery();

        AssertStuff();
    }
}

public void InterceptCloudTableQueryExecute<T>(IEnumerable<T> result)
{
    var query = result.AsQueryable();

    ShimCloudTableQuery<T>.AllInstances.Execute = (instance) =>
    {
        // Get the expression evaluator.
        MethodCallExpression ex = (MethodCallExpression)instance.Expression;

        // Depending on how I called CreateQuery, sometimes the objects
        // I need are nested one level deep.
        if (ex.Arguments[0] is MethodCallExpression)
        {
            ex = (MethodCallExpression)ex.Arguments[0];
        }

        UnaryExpression ue = ex.Arguments[1] as UnaryExpression;

        // Get the lambda expression
        Expression<Func<T, bool>> le = ue.Operand as Expression<Func<T, bool>>;

        query = query.Where(le);
        return query;
    };
}