When running a test list in which a parent test calls a subtest with a coded step you may get the following: Overall Result: Fail ------------------------------------------------------------ '11/21/2014 10:10:33 AM' - Executing test: 'ExecuteTestAsStep', path: 'ExecuteTestAsStep.tstest.' '11/21/2014 10:10:33 AM' - Using .Net Runtime version: '4.0.30319.18444' for test execution. Build version is '2014.3.1016.0'. '11/21/2014 10:10:33 AM' - Starting execution.... ------------------------------------------------------------ ------------------------------------------------------------ '11/21/2014 10:10:35 AM' - Enabling Html Popup Tracker. Test expecting Popups. '11/21/2014 10:10:35 AM' - Using 'InternetExplorer' version '10.0' as default browser. '11/21/2014 10:10:35 AM' - 'Fail' : 1. Execute test 'AccessWebsite' >>> Test-as-Step 'AccessWebsite.tstest' log starts: ------------------------------------------------------------ '11/21/2014 10:10:35 AM' - Detected custom code in test. Locating test assembly: CommandLineClientExecutionErrorSample.dll. '11/21/2014 10:10:35 AM' - Assembly Found: F:\TEMP\Projects\ed08cc31-39a7-4e41-b982-3cc9af2cfda7\CommandLineClientExecutionErrorSample\bin\CommandLineClientExecutionErrorSample.dll '11/21/2014 10:10:35 AM' - Loading code class: 'CommandLineClientExecutionErrorSample.AccessWebsite'. ------------------------------------------------------------ '11/21/2014 10:10:35 AM' - Error attempting to execute a Test As Step. Details: '11/21/2014 10:10:35 AM' - System.ArgumentException: Unable to find the test class type 'CommandLineClientExecutionErrorSample.AccessWebsite' in your test assembly. Please make sure your test code behind is compiled with your latest changes. at ArtOfTest.WebAii.Design.Execution.ExecutionUtils.EnsureTypeExists(Assembly assm, String typeName) at ArtOfTest.WebAii.Design.Execution.ExecutionUtils.CreateCodedTestInstance(Test test, TestResult result, String binariesFolder) at ArtOfTest.WebAii.Design.Execution.ExecutionEngine.InternalExecuteTest(Test test, TestResult initializationResult) at ArtOfTest.WebAii.Design.Execution.ExecutionEngine.ExecuteTestInCurrentContext(Test test) <<< Test-as-Step 'AccessWebsite.tstest' log ends. ------------------------------------------------------------ '11/21/2014 10:10:35 AM' - Detected a failure. Step is marked 'ContinueOnFailure=False' aborting test execution. ------------------------------------------------------------ '11/21/2014 10:10:35 AM' - Overall Result: Fail '11/21/2014 10:10:35 AM' - Duration: [0 min: 0 sec: 121 msec] ------------------------------------------------------------ '11/21/2014 10:10:35 AM' - Test completed! Sample project to reproduce the problem is attached. Run it from command line using: "c:\Program Files (x86)\Telerik\Test Studio\Bin\Telerik.TestStudio.CommandLineClient.exe" -l TestLists\SampleList.aiilist -u http://localhost:8009