CODEWITHSUNDEEP
c#unit-testing
vibhu
vibhu

Reputation: 1705

Mock IDataReader Extension Method

I am thinking to mock an extension method (used in project) over IDataReader. I want to return a test data collection when ReadAll() (below) is called.

public static IEnumerable<object[]> ReadAll(this IDataReader reader)
{
    while (reader.Read())
    {
        var values = new object[reader.FieldCount];
        reader.GetValues(values);
        yield return values;
    }
}

I am aiming to return a custom IEnumerable<object[]> collection. I mocked Read() method by checking the count against the custom collection, 

int count = -1;
var testData = ReadData(); //Custom collection
DataReaderInfoMock.Setup(x => x.DataReader.Read()).Returns(() => count < testData.Count() - 1).Callback(() => count++);

However, I cannot think of way to mock implementation under Read() block, if at all that is possible.

Is there any way I could test it?

Upvotes: 2

Views: 956

Answers (1)

Pidon
Pidon

Reputation: 275

You can't mock an extension method, but you could write your own implementation of IDataReader to use as a mock.

Like so (I only wrote the methods you need, IDataReader has many more):

class MockDataReader : IDataReader
{
    private List<object[]> _data;
    private int _current = -1;

    public MockDataReader(List<object[]> data)
    {
        _data = data;
    }

    public int FieldCount
    {
        get
        {
            return _data.FirstOrDefault()?.Length ?? 0;
        }
    }

    public int GetValues(object[] values)
    {
        object[] record = _data[_current];

        for (int i = 0; i < record.Length; i++)
        {
            values[i] = record[i];
        }

        return record.Length;
    }

    public bool Read()
    {
        _current++;

        return _current < _data.Count;
    }
}

Upvotes: 2

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