If I'm developing something for the web and I've already done functional testing in Chrome, Firefox, and IE on Windows do I really need to do the same on OS X? Are the browsers (Chrome and Firefox) widely different in how they work between each operating system that separate tests are needed in each browser for each OS?
webgl for example, is implemented with angel on windows. angel is based on directx. there could be differences. I have a concrete example, but it is a long story. I'm too lazy to type. I might be able to find the link.
chrome video decoding is another example. on windows, you might be using hardware decoder. on mac, that could be a different story.
browser sandbox is also platform dependent.
depends on what you are testing. a thorough test might require you to test it on different versions of macs even. but that costs money and time.
True. But since Safari can't be put on Windows I didn't include it as part of my question.
But say I did all my testing on Mac (except IE); does Chrome behave that differently between OS X and Windows that it should be tested on both? Same for Firefox?
From my experience you're OK like 90% of the time. Sometimes fonts look a little different, etc, but generally you're OK.
I agree with the grandparent though, you need to worry more about Safari because of the iPhone users that hit your site. Case in point I recently saw a site work perfectly on in all major browsers on the desktop, but Safari would get caught in a loop of repainting. The result was a webpage that looked like it hung the browser, but it was actually taking like a minute to finish rendering the page.
No doubt, Safari is tested fully. I was just curious why I would want to test Chrome on both a Mac and Windows for general web stuff; same with Firefox (since Safari can't be put on Windows).
Most places probably don't test the same browser on both unless they have a specific bug report they can't reproduce on their normal testing platform.
Given the popularity of Macs with web/front end developers, and the ease (+ legality) of running windows on Mac (vs Mac on windows), most developers end up testing ff,chrome,opera,etc on OS X and use vm(s) for ie - often the ms provided ie testing vms.
chrome video decoding is another example. on windows, you might be using hardware decoder. on mac, that could be a different story.
browser sandbox is also platform dependent.
depends on what you are testing. a thorough test might require you to test it on different versions of macs even. but that costs money and time.