/usr/share/cups/templates/test-page.tmpl is in cups-server-common 1.7.2-0ubuntu1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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<H2 CLASS="title">Print Test Page On {printer_name}</H2>
<P>Test page sent; job ID is <A HREF="/{SECTION}/{printer_name}">
{printer_name}-{job_id}</A>.</P>
</DIV>
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