I am getting two Test Failed message when trying to upgrade from 2.0.15 to 2.0.16.
The failures are with the ./Sources/QueryString.php

This line is editable.
The problem is with the other test failure:

When editing the file I cannot locate the line:
$buffer = preg_replace_callback('~"' . preg_quote($scripturl, '/') . '\?((?:board|topic)=[^#"]+?)(#[^"]*?)?"~', 'pathinfo_insert__preg_callback', $buffer);
}and I get a "Can't find the text" error with my text editor.
You probably have a modified QueryString.php file
That second edit isn't required if you have a new/updated theme. It fixes a loginbox issue on some older themes.
Thanks. I just edited the first test failure, and the upgrade installed with no problems.