Add the testbed to "Favorites" view and then you will see the list of devices in the testbed.
Then Click on "Start Capture" button in the main toolbar.
You can double click on a device node in Favorites view to start the session. You can start as many sessions as you want to different devices.
When you are done, click on "Finish Capture" button on the main toolbar and a wizard will popup helping you put steps into a testcase of your choice.
Just something to note:
iTest captures all your sessions all the time. "Start Capture" and "Finish capture" are simply ways to denote a time interval between which all captured actions are put into a testcase using a friendly wizard.
You can at any time open "Capture" view and drag and drop items from there into any testcase (new or existing) at any time to create a new testcase. In fact, once you get comfortable with this approach, you may find that this may be more powerful than using "Start Capture" button.
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