UnitTesting PatIndex

Question

when unit testing PatIndex of SqlFunctions with a mocked IQueryable object I'm getting the following error:

"This function can only be invoked from LINQ to Entities."

Here is how I initialize my mock repositories:

protected void InitUnitOfWork<TEntity>(IEnumerable<TEntity> data)
    where TEntity : class
{
    var dataSet = Substitute.For<IDbSet<TEntity>, IQueryable<TEntity>>().Initialize(data.AsQueryable());
    var query = Substitute.For<IRepositoryQuery<TEntity>>();
    var repository = Substitute.For<IRepository<TEntity>>();

    this.UnitOfWork.Repository<TEntity>().Returns(repository);
    repository.Query().Returns(query);
    query.Include(null).ReturnsForAnyArgs(query);
    query.Filter(null).ReturnsForAnyArgs(query);
    query.Get().Returns(dataSet);
}

This is the method I'm trying to test:

public IEnumerable<ContactDto> GetContactsBySearchText(string searchText)
{
    var companyId = CurrentUser.User.CurrentCompany.Id;

    var contacts = this.GetIQueryableContacts().Where(x => x.CompanyMasterData.Id == companyId);

    if (!string.IsNullOrWhiteSpace(searchText))
    {
        var pattern = SearchQueryParserHelper.ParseString(searchText.Trim());
        contacts = contacts.Where(x => SqlFunctions.PatIndex(pattern, x.Name) > 0
            || SqlFunctions.PatIndex(pattern, x.Code) > 0
            || SqlFunctions.PatIndex(pattern, x.Phone) > 0);
    }

    return Mapper.Map<IQueryable<Contact>, IEnumerable<ContactDto>>(contacts);
}

I know I can fix this issue by using the database, but how can I mock it correctly?

I'm using NSubstitute as Mocking Framework.

Best regards

Daniel

Answer 1

Make use of Microsoft.QualityTools.Testing.Fakes.dll (Here is the link on how to use it: MSDN)

Later on generate Fakes assembly for System.Data.Entity.SqlServer.dll

Wrap the body of your Unit Test method following using statement:

using (Microsoft.QualityTools.Testing.Fakes.ShimsContext.Create())
{
     // Setup Shim function for PatIndex:
     System.Data.Entity.SqlServer.FakesShimSqlFunctions.PatIndexStringString = (pattern, target) => 
     {
        // Implement PatIndex function here
        throw new NotImplementedException();
     }

     // Your Unit test code goes here
}

Once you have provided a Shim (you can call it as a replacement) for PatIndex, you will be able to unit test your target method successfully.