Visual Studio Load Testing - unique data each time - visual-studio-2013

Question

I am using Visual Studio Ultimate 2013 to do some load tests. I have some test data attached to my web test, with 10,000 rows of unique data, and i also have a web test plugin in another project, which i have referenced. in the web test.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Microsoft.VisualStudio.QualityTools.WebTestFramework;
using Microsoft.VisualStudio.TestTools.WebTesting;
namespace VUControl
{
public class VUControl : WebTestPlugin
{
public override void PreWebTest(object sender, PreWebTestEventArgs e)
{
base.PreWebTest(sender, e);
e.WebTest.MoveDataTableCursor("testdata", "strictly#csv", e.WebTest.Context.WebTestUserId);
}
}
}
I have set the Source table properties to 'Do not move cursor automatically'.
The load test is set to run on the cloud, running for 5 minutes with 500 users.
On running the tests, i am getting around 9500 tests completing succesfully, but i am only getting around 10 unique sets of data generated in the database.
The page i am testing is essentially a registration page on a web site.
can anyone tell me why i would only see 10 random selections of data appear?

Answer 1

I would guess that you have 10 load generators? Or maybe a max of 10 threads?
The real problem, in my humble opinion, is that the MoveDataTableCursor() method works in a stand alone webtest, but NOT when that same web or API test is included in a load test. You can workaround this issue by implementing a row count for your dataset, like so:
// datasetRowNumber is a pointer to the row number of an in-memory copy of the dataset. Each agent has a copy of the dataset.
static int datasetRowNumber;
public override void PreWebTest(object sender, PreWebTestEventArgs e)
{
int totalAgentCount = e.WebTest.Context.AgentCount; // Used in a modulus operation to skip rows in the dataset
int agentID = e.WebTest.Context.AgentId; //Used in conjunction with totalAgentCount in the modulus operation
while ((datasetRowNumber++ % totalAgentCount) != (e.WebTest.Context.AgentId - 1))
{
// We have incremented datasetRowNumber in the line above.
// Here is where we will use it to point to the new row.
e.WebTest.MoveDataTableCursor(DSName, tableName, datasetRowNumber);
}
string dataValue = e.WebTest.Context["DataSource1.SampleData.PRNCode"].ToString();
// Logging. Comment this out during a load test!
// writer.WriteToLog("Value=" + dataValue + ", TotalAgentCount=" + e.WebTest.Context.AgentCount + ", AgentID=" + e.WebTest.Context.AgentId + ", Iteration=" + iteration);
}
The above code is an implementation of the code in the following blog:
https://blogs.msdn.microsoft.com/slumley/2008/03/14/description-of-access-methods-in-data-sources/. Sean Lumley's "Description of Access Methods" works great for a web test, but when placed into a load test, the MoveDataTableCursor() method does not work as expected.
The above code makes use of the overload for MoveDataTableCursor()
described subtlety in https://blogs.msdn.microsoft.com/slumley/2010/01/04/vsts-2010-feature-data-source-enhancements
Without the datasetRowNumber variable, Slumley's code does not advance the cursor in a load test; in Lumley's version, the cursor advancement only works in a stand-alone webtest.