Good news! You don't have to write the whole test again. You can just configure the ixia box again the way you want using IxExplorer and then open a new ixia session and issue a “configuration save <filename>” command. You can either set the ixia session profile to point to the new configuration file, or copy the contents and change the body of your “configure” step in the test case.
For minor changes(e.g. changing the frame size), you could even change the configuration manually. Hope this helps.
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