I cannot check it out myself (I'm not a MacOS user), bit iGetter seems to be what you're after:
iGetter is a powerful, full featured download manager and accelerator. iGetter can greatly improve the speed of your downloads using segmented downloading. In addition it allows auto resume on broken downloads, queue filtering by various criteria, site explorer, history list, scheduling downloads for low traffic periods, auto redial on broken connection, auto hang-up and shut down on completion, and much more.
- supports resume: Yes, even automatically. But as with any such tools, servers must support this as well (if a server doesn't, iGetter will inform you on the fact)
- check whether download was successful: That's part of the resume process :)
Additional features of interest:
- supports multiple sources ("mirrors") for the same file to speed up downloading ("download accelerator", "segmented downloading")
- a nice GUI lets you follow the progress and organize your downloads
- scheduled downloads: tell it when to go for it :)
- site explorer to investigate remote ftp or http sites

iGetter screenshots: scheduler, download manager, segmented downloading (source: iGetter; click images for larger variants)
http downloader mac-os resume
, by the way :) – Izzy♦ Apr 28 '15 at 11:08