If you have to set the Clipboard text programmatically in your Windows Phone, you can use the Clipboard Class that is defined in the System.Windows Namespace.
Clipboard is a static class that exposes 3 properties
How to Set Clipboard text (Copy Paste) programmatically in Windows Phone?
You can use the Clipboard.SetText to set the text for the clipboar.
There is also a restriction to use the Clipboard.GetText which results in the SecurityException.
To test if the Clipboard has the value that you set, just paste the data to a textbox after using the Clipboard.SetText