I am looking for a Microsoft Windows 7 emulator for Mac platform.
I would not mind how restrictive it is, I just need Chrome/IE/Firefox on Windows 7 for testing purposes.
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You should be able to use Wine on Mac. It should work on Intel Macs - older PowerPC Macs won't work. It can run Firefox and Chrome/Chromium, as well as Internet Explorer up to version 8. 32bit applications work best, only some 64bit may run - it will works Windows XP by default, you can change to Windows 7 in settings.
As someone who does not use Windows much, I have found that for testing in newer versions of Internet Explorer (9+) you will need to run a Windows VM as suggested in @SteveBarnes, if you do not have a actual Windows machine available. Newer versions can to some extent simulate older versions I think as well.
https://dev.modern.ie/ offer free download of various virtual machines XP through 10 with IE 6-11 & Edge for testing on Windows, OS-X & Linux & for various VM bases. They are time limited but can be reinstalled.
The site has now moved to https://developer.microsoft.com/en-us/microsoft-edge/tools/vms/ but currently (October 2020) offers VMs for Win7/8/10 with specific browsers to test use.