How to mock an SqlDataReader using Moq - Update

Question

I'm new to moq and setting up mocks so i could do with a little help. How do I mock up an SqlDataReader using Moq?

Update

After further testing this is what I have so far:

private IDataReader MockIDataReader() {     var moq = new Mock<IDataReader>();     moq.Setup( x => x.Read() ).Returns( true );     moq.Setup( x => x.Read() ).Returns( false );     moq.SetupGet<object>( x => x["Char"] ).Returns( 'C' );      return moq.Object; }  private class TestData {     public char ValidChar { get; set; } }  private TestData GetTestData() {    var testData = new TestData();     using ( var reader = MockIDataReader() )    {        while ( reader.Read() )        {            testData = new TestData            {                ValidChar = reader.GetChar( "Char" ).Value            };        }    }     return testData; } 

The issue you is when I do reader.Read in my GetTestData() method its always empty. I need to know how to do something like

reader.Stub( x => x.Read() ).Repeat.Once().Return( true )  

as per the rhino mock example: Mocking a DataReader and getting a Rhino.Mocks.Exceptions.ExpectationViolationException: IDisposable.Dispose(); Expected #0, Actual #1

Answer 1

Moq has an ability to run some code after the method is executed. It is called "Callback". Modify your code this way and it will work:

private IDataReader MockIDataReader() {     var moq = new Mock<IDataReader>();      bool readToggle = true;      moq.Setup(x => x.Read())          // Returns value of local variable 'readToggle' (note that           // you must use lambda and not just .Returns(readToggle)           // because it will not be lazy initialized then)         .Returns(() => readToggle)          // After 'Read()' is executed - we change 'readToggle' value          // so it will return false on next calls of 'Read()'         .Callback(() => readToggle = false);       moq.Setup(x => x["Char"])         .Returns('C');      return moq.Object; }  private class TestData {     public char ValidChar { get; set; } }  private TestData GetTestData() {     var testData = new TestData();      using ( var reader = MockIDataReader() )     {        testData = new TestData        {            ValidChar = (Char)reader["Char"]        };    }     return testData; } 

But what if it will be required IDataReader to contain not only single row, but several? Well, here is a sample:

// You should pass here a list of test items, their data // will be returned by IDataReader private IDataReader MockIDataReader(List<TestData> ojectsToEmulate) {     var moq = new Mock<IDataReader>();      // This var stores current position in 'ojectsToEmulate' list     int count = -1;      moq.Setup(x => x.Read())         // Return 'True' while list still has an item         .Returns(() => count < ojectsToEmulate.Count - 1)         // Go to next position         .Callback(() => count++);      moq.Setup(x => x["Char"])         // Again, use lazy initialization via lambda expression         .Returns(() => ojectsToEmulate[count].ValidChar);      return moq.Object; } 

Answer 2

I was just trying to figure this out myself. Not sure if this is new functionality in Moq, but it appears there is a simpler way than @Monsignor's answer.

Use Moq's SetupSequence method. Your code simply becomes:

private IDataReader MockIDataReader() {     var moq = new Mock<IDataReader>();     moq.SetupSequence( x => x.Read() )        .Returns( true )        .Returns( false );     moq.SetupGet<object>( x => x["Char"] ).Returns( 'C' );      return moq.Object;  }