How to mock IDataReader to test a method that converts SqlDataReader to System.DataView

Question

I'm new to Moq, and I'm struggling to write Unit Test to test a method that converts SqlDataAdapterto System.DataView. This is my method:

private DataView ResolveDataReader(IDataReader dataReader)
{
    DataTable table = new DataTable();

    for (int count = 0; count < dataReader.FieldCount; count++)
    {
        DataColumn col = new DataColumn(dataReader.GetName(count), 
                                        dataReader.GetFieldType(count));
        table.Columns.Add(col);
    }

    while (dataReader.Read())
    {
        DataRow dr = table.NewRow();
        for (int i = 0; i < dataReader.FieldCount; i++)
        {
            dr[i] = dataReader.GetValue(dataReader.GetOrdinal(dataReader.GetName(i)));
        }
        table.Rows.Add(dr);
    }

    return table.DefaultView;
}

I am trying to create something like:

var dataReaderMock = new Mock<IDataReader>();
var records = new Mock<IDataRecord>();
dataReaderMock.Setup(x => x.FieldCount).Returns(2);
dataReaderMock.Setup(x => x.Read()).Returns(() => records);

I would like to pass some data and make sure that it is converted.

Thanks.

Answer 1

You were on the right track with your bullying, but dataReaderMock.Setup(x => x.Read()).Returns(() => records);this is where you were wrong, because it .Readreturns bool, not the records themselves, which are read using IDataReaderyour method.

---

:

var dataReader = new Mock<IDataReader>();
dataReader.Setup(m => m.FieldCount).Returns(2); // the number of columns in the faked data

dataReader.Setup(m => m.GetName(0)).Returns("First"); // the first column name
dataReader.Setup(m => m.GetName(1)).Returns("Second"); // the second column name

dataReader.Setup(m => m.GetFieldType(0)).Returns(typeof(string)); // the data type of the first column
dataReader.Setup(m => m.GetFieldType(1)).Returns(typeof(string)); // the data type of the second column

, , .. , , , GetName GetFieldType .

.Read(), SetupSequence:

dataReader.SetupSequence(m => m.Read())
    .Returns(true) // Read the first row
    .Returns(true) // Read the second row
    .Returns(false); // Done reading

, :

private const string Column1 = "First";
private const string Column2 = "Second";
private const string ExpectedValue1 = "Value1";
private const string ExpectedValue2 = "Value1";

private static Mock<IDataReader> CreateDataReader()
{
    var dataReader = new Mock<IDataReader>();

    dataReader.Setup(m => m.FieldCount).Returns(2);
    dataReader.Setup(m => m.GetName(0)).Returns(Column1);
    dataReader.Setup(m => m.GetName(1)).Returns(Column2);

    dataReader.Setup(m => m.GetFieldType(0)).Returns(typeof(string));
    dataReader.Setup(m => m.GetFieldType(1)).Returns(typeof(string));

    dataReader.Setup(m => m.GetOrdinal("First")).Returns(0);
    dataReader.Setup(m => m.GetValue(0)).Returns(ExpectedValue1);
    dataReader.Setup(m => m.GetValue(1)).Returns(ExpectedValue2);

    dataReader.SetupSequence(m => m.Read())
        .Returns(true)
        .Returns(true)
        .Returns(false);
    return dataReader;
}

_{( Setup, - dataReader , )}

. :

[Test]
public void ResovleDataReader_RowCount()
{
    var dataReader = CreateDateReader();
    var view = ResolveDataReader(dataReader.Object);
    Assert.AreEqual(2, view.Count);
}

[Test]
public void ResolveDataReader_NamesColumn1()
{
    var dataReader = CreateDataReader();
    var view = ResolveDataReader(dataReader.Object);
    Assert.AreEqual(Column1, view.Table.Columns[0].ColumnName);
}

[Test]
public void ResolveDataReader_PopulatesColumn1()
{
    var dataReader = CreateDataReader();
    var view = ResolveDataReader(dataReader.Object);
    Assert.AreEqual(ExpectedValue1, view.Table.Rows[0][0]);
}

// Etc..

_{( NUnit, assert )}

---

, , , ResolveDataReader internal InternalsVisibleTo, , , , .

Answer 2

IDataReader mock:

public static class DataReaderMock
{
    public static void SetupDataReader(this Mock<IDataReader> mock, ICollection<string> columns, object[,] values)
    {
        if (columns.Count != values.GetLength(1))
        {
            throw new ArgumentException($"The number of named columns must be identical to the number of columns in the 2d values array: {columns.Count} compared to {values.GetLength(1)}");
        }
        mock.Setup(reader => reader.FieldCount).Returns(columns.Count);

        var setupSequence = mock.SetupSequence(reader => reader.Read());
        var callbacks = new List<Action<object[]>>
        {
            vals => vals.Populate(columns.Cast<object>().ToList())
        };
        for (var row = 0; row < values.GetLength(0); row++)
        {
            var currentRow = row; // for closure
            callbacks.Add(vals => vals.Populate(values, currentRow));
            setupSequence.Returns(true);
        }
        setupSequence.Returns(false);
        mock.Setup(reader => reader.GetValues(It.IsAny<object[]>())).CallbackSequence(callbacks.ToArray());
    }

    private static void Populate<T>(this IList<T> target, IList<T> source)
    {
        for (var i = 0; i < target.Count; i++)
        {
            target[i] = source[i];
        }
    }

    private static void Populate<T>(this IList<T> target, T[,] sourceTable, int row)
    {
        for (var i = 0; i < sourceTable.GetLength(1); i++)
        {
            target[i] = sourceTable[row, i];
        }
    }

    private static void CallbackSequence<T, TResult, TArg>(this ISetup<T, TResult> setup, params Action<TArg>[] callbacks) where T : class
    {
        var queue = new ConcurrentQueue<Action<TArg>>(callbacks);
        setup.Callback((TArg arg) =>
        {
            Action<TArg> callback;
            if (!queue.TryDequeue(out callback))
            {
                Assert.Fail("More callbacks were invoked than defined in sequence");
            }
            callback(arg);
        });
    }
}

:

const int ItemsCount = 1000;
var dataReaderMock = new Mock<IDataReader>();
var values = new object[ItemsCount, 2];
for (var i = 0; i < ItemsCount; i++)
{
    values[i, 0] = i + 1;
    values[i, 1] = (i + 1).ToString();
}
dataReaderMock.SetupDataReader(new List<string> {"Col1", "Col2"}, values);