How to maintain state in a data-driven unit test

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Imagine you need to maintain a list of processed data rows in a running data-driven unit test. Well, you can use the code below as a starting point:

[DataSource(
"System.Data.SqlClient", "Data Source=.;Initial
Catalog=FeatureDemo;Integrated Security=True",
"Person",
DataAccessMethod.Sequential),
TestMethod(),]
public void Test()
{
if (!TestContext.Properties.Contains("Session"))
{
TestContext.Properties["Session"] = Guid.NewGuid();
}
Guid session = (Guid)TestContext.Properties["Session"];
// Now add your unit test code here
// ...
}

TestContext is the way to go in order to maintain state during one test instance. The main point here is that a data-driven test is viewed as a single test instance (although the test method is called many times for each row of the data table).

You can also use the above unit test in a load test scenario knowing that the state of each logical load test thread is maintained independently.