What are the most recent set of software tools that are known to work on OSX Sierra?
Any pointers to a good IDE for debugging will be great. I understand there are many questions on the forum related to this topic, but posting this question to get the latest information.
Segger Embedded Studio. I really wouldn't even bother with anything else.
Personally, I don't use an IDE (but OS/X). If I had to, I would have a look into Eclipse.
As a user of IDEs and OSX I wouldn't recommend anyone use Eclipse for embedded development if they have any other choice or unless they are a heavy Eclipse user in general and want to stay on one platform.
Given that SES is now free for even commercial Nordic development, the SDK comes with SES projects in it as well as Keil and IAR and GCC so it's fully supported and licensed by Nordic, it was written for embedded development, not just had it tacked on badly as Eclipse did and works natively with Segger, not via the terrible GDBServer interface it's hard to find a good reason not to use it.
As RK said, I would really recommend you to try SEGGER Embedded Studio.
There is a video tutorial series on youtube with an intro to using SES with the new SDK, that you can take a look at.
Getting started with SEGGER Embedded Studio and the nRF5 SDK
Are you writing unit tests that are running on your development machine? Would this be covered by SES too? Looks like I have to look into SES once.