Planning to test our web application in Safari/Windows 7 instead of Safari/OS X & iOS
Safari for Windows was dropped at version 6, in 2012. It is no longer available for download, directly from Apple, though can be found on several file hosters.
The last version of Safari for Windows was 5.1.7, released May 9, 2012.

I would say testing against such an outdated version would not really be useful at all.

There's a long article on resurrecting it for Windows 10 here though it doesn't deal with the comparison in security or real compatibility terms.