Visual Studio 2010 Ultimate Web Performance Test and Load Test Virtual User Accounts

Question

I need to Load Test a website. It uses Crowd Authentication for users to authenticate against.

I have created a Visual Studio 2010 Test Project and created a web performance test that signs in using the username and password I used when I recorded the test. I have attached an access database with a table called Users in it that I have bound to the login form and the test suite runs a test for each row of data in the users table.

This is all working as I would expect.

Now I want to run a Load Test with the maximum 250 concurrent users. How do I tell Visual Studio to use a different username and password for each of the Virtual Users in the Load Test.

In short I want to set up a profile for each Virtual User in the Load Test.

Answer 1

I would create a web test that uses only one login at a time to login. Then you can either create a small piece of code in the webtest to get a "random" login from the database a list in code to select the login.

If you require a unique login for each test, you will have to estimate how many logins are required and prepopulate that many.

The issue with selecting from a database is that virtual users share threads and any blocking code in a test will block more than one virtual user. It is possible to create a list in memory that holds all the login details, but manageing a shared object in a highly multithreaded environment require care.

For us, we created a stored procedure that would get the next login password and username and then called the following method to get the next login.

   public static bool GetNextLogin(out string userName, out string password)
    {
        bool result = false;

        using (SqlConnection connection = new SqlConnection(loadTestLoginsConnection))
        {
            using (SqlCommand command = new SqlCommand("GetNextID", connection))
            {
                connection.Open();
                using (SqlDataReader reader = command.ExecuteReader())
                {
                    while (reader.Read())
                    {
                        userName = reader["UserName"].ToString().Trim();
                        password = reader["Password"].ToString().Trim();
                        result = true;
                    }
                }
            }
        }

        return result;
    }

This worked without problems for us and the returned values could be added to the correct form post parameter. If you are using normal authentication, the same code can be used in the load test constructor to change the WebTest.UserName and WebTest.Password properties.

Our stored procedure worked on a list of available logins and a table with one int field called CurrentLoginID

BEGIN TRANSACTION
        BEGIN TRY
            DECLARE @CurrentID AS INT
                UPDATE CurrentLoginID SET Number = Number+1
                SELECT @CurrentID = Number FROM CurrentLoginID
                SELECT [Password], UserName FROM AvailableLogins WHERE AvailableLogins.ID = @CurrentID
            COMMIT
            END TRY
        BEGIN CATCH
                DECLARE @ErrorMessage NVARCHAR(4000);
                DECLARE @ErrorSeverity INT;
                DECLARE @ErrorState INT;

                SELECT 
                    @ErrorMessage = ERROR_MESSAGE(),
                    @ErrorSeverity = ERROR_SEVERITY(),
                    @ErrorState = ERROR_STATE();

                -- Use RAISERROR inside the CATCH block to return error
                -- information about the original error that caused
                -- execution to jump to the CATCH block.
                RAISERROR (@ErrorMessage, -- Message text.
                           @ErrorSeverity, -- Severity.
                           @ErrorState -- State.
                           );
            ROLLBACK TRAN                 
        END CATCH