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Asked: 2026-05-11T14:56:27+00:00

I’m trying to unit test a few .NET classes that (for good design reasons)

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I’m trying to unit test a few .NET classes that (for good design reasons) require DbConnections to do their work. For these tests, I have certain data in memory to give as input to these classes.

That in-memory data could be easily expressed as a DataTable (or a DataSet that contains that DataTable), but if another class were more appropriate I could use it.

If I were somehow magically able to get a DbConnection that represented a connection to the in-memory data, then I could construct my objects, have them execute their queries against the in-memory data, and ensure that their output matched expectations. Is there some way to get a DbConnection to in-memory data? I don’t have the freedom to install any additional third-party software to make this happen, and ideally, I don’t want to touch the disk during the tests.

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  1. Rather than consume a DbConnection can you consume IDbConnection and mock it? We do something similar, pass the mock a DataSet. DataSet.CreateDataReader returns a DataTableReader which inherits from DbDataReader.

    We have wrapped DbConnection in our own IDbConnection-like interface to which we’ve added an ExecuteReader() method which returns a class that implements the same interfaces as DbDataReader. In our mock, ExecuteReader simply returns what DataSet.CreateDataReader serves up.

    Sounds kind of roundabout, but it is very convenient to build up a DataSet with possibly many resultsets. We name the DataTables after the stored procs that they represent the results of, and our IDbConnection mock grabs the right Datatable based on the proc the client is calling. DataTable also implements CreateDataReader so we’re good to go.

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