Handling Exceptions in Scripts

JavaScript, JScript, C#Script and C++Script

Python

VBScript

DelphiScript

Exceptions That Occur in the Application Under Test

To handle exceptions in JavaScript and JScript use the try{}…catch{}…finally{} statement. catch holds code that is executed when an exception occurs within the try block. finally contains instructions which are executed always, regardless of whether or not exceptions occur in the try block. For more information see the description of the try...catch statement in the JavaScript documentation or the description of the try...catch...finally statement in the JScript documentation. The following code demonstrates how you can handle exceptions in JavaScript routines:

Since C#Script and C++Script are based on JScript, you can use the same try... catch... finally statement. For example:

Although TestComplete supports cross-unit exception handling, there are some limitations:

• In JavaScript, there may be issues with determinig of the error’s type. For more information, see JavaScript - Specifics of Usage.

• In JScript, C#Script and C++Script, in certain cases, the try...catch...finally statement cannot catch and handle exceptions that were raised in different units. For more information, see JScript, C#Script and C++Script - Specifics of Usage.

To handle exceptions in Python, use the try…except…else…finally statement.

The except block is executed when an exception occurs within the try block.

The optional else block is executed only if there were no exceptions after try and before finally.

The finally block contains instructions that are always executed at the end, regardless of whether exceptions occurred in the try block.

For more information, see the description of https://docs.python.org/3.6/tutorial/errors.html exceptions in the Python documentation. The code below demonstrates how you can handle exceptions in Python routines:

def test():
  try:
    # Do something
    ...
  except Exception as e:    
    Log.Error(str(e))
  else:
    # Do something else if there were no errors
    # You can handle other potential exceptions here:
    try:
      ...
    except Exception as e:    
      Log.Error(str(e))
    ...
  finally:
    # Finalize the run
    ...

To handle exceptions, you can use the Err object and the On Error statement. To learn more about them, refer to the description of the Err object and of the On Error statement in the VBScript documentation in the MSDN Library. The following code demonstrates how you can handle exceptions in VBScript routines:

To cancel the effect of the On Error Resume Next statement, call On Error GoTo 0.

Methods that handle exceptions in DelphiScript are similar to those that handle exceptions in Delphi. This includes the try... except... end and try... finally... end statements. These statements handle exceptions that occur within the try... except and try... finally blocks.

The except... end block is executed only if an exception occurs. Use it to perform specific actions as a response to an exception. If no exceptions occur, the control is passed to the instruction next to the end statement.

The finally... end block is always executed. Use it to ensure that certain operations in your code are completed whether or not exceptions occur.

To obtain the exception message in scripts, use the ExceptionMessage function. The following code illustrates exception handling in DelphiScript routines:

If you have recursive code in the try block, after TestComplete exits the recursive loop, it will run the code in the except block regardless of whether any errors have occurred in the try block or not.

TestComplete can handle exceptions that occur in the application under test, but this is only possible if the tested application is an Open Application. To handle these exceptions use the same statements that you use to handle exceptions in your scripts (since calls to Open Application’s methods do not differ from calls to any other script functions). These statements are language-specific and they were described in the previous sections of this topic. However, there are some specifics:

• TestComplete handles exceptions only when the script calls methods or properties of an application object. This is not possible with ordinary “closed” applications. Suppose that an exception occurs after pressing a button on a form. TestComplete will handle this exception if the script simulates the keystroke using the following instruction:

  w.VCLObject('Button1').NativeDelphiObject.Click;

  TestComplete will not handle the exception, if you use the following code to simulate the button pressing:

  w.VCLObject('Button1').Click(); // Exception is not handled !!!

• If an exception occurs during a method call made through the Debug Info Agent™ (the methods called through the Agent are displayed under the Debug Agent node in the Object Browser), the scripting engine’s behavior depends on the Advanced exception handling property of your TestComplete project. If this property is enabled, then the scripting engine receives notification about the exception and the exception-handling statements (try/catch, try/except, etc.) come into play. If the property is disabled (default), the exception is hidden and the method returns a null value (0, null reference, empty string and so on). This mode is used for compatibility with earlier TestComplete versions. You can enable the project’s Advanced exception handling property if you do not run legacy projects. You can also control the property’s state from scripts by using the DebugAgent.AdvancedExceptionHandling property.

An exception that occurs in the application under test usually acts as an unexpected window in TestComplete (this exception message box is unexpected,  because it did not appear when the script was being recorded). Using project settings of the Playback group and the OnUnexpectedWindow event handler, you can handle unexpected windows in the desired way. For more information, see Handling Unexpected Windows. This way applies to both “Open” and “black-box” applications.

To view the call stack for exceptions, you can use the DbgServices object. If a tested application is launched by one of the methods of this object, TestComplete will trace errors and exceptions in this application and if an exception occurs, TestComplete will show the call stack for it in the test log. See Tracing Events and Exceptions With Debug Services. This approach also works for both “Open” and “black-box” applications.