libfaketime

libfaketime is useful for testing these kinds of things. It intercepts system calls to get the time and reports a fake time to the application. https://github.com/wolfcw/libfaketime

I would mock/hook/monkey patch/whatever the functions to get the current time/elapsed time, simulate a period of time (a day/week/month/year/whatever), make sure the function to download the file is called the correct amount of times. That would probably catch this bug. Although, after such a fuck up, I would be tempted to make a pre-release check that tests the compiled binary, not any unit test or whatever. Use LD_PRELOAD to hook the system timing functions(a quick google shows that libfaketime[0] exists, but I've never used it), launch the real program and speed up time to make sure it doesn't try to download more than once. [0] https://github.com/wolfcw/libfaketime

The easiest way to do this (in my experience) is libfaketime. I'm surprised not to see it mentioned. https://github.com/wolfcw/libfaketime

I can recommend libfaketime regarding this topic. It can bei used to change the system time for a single application only. https://github.com/wolfcw/libfaketime

Not a mock obviously but in the interest of getting things done on schedule I’d suggest running tests in a container with https://github.com/wolfcw/libfaketime and orchestrating edge cases like leap seconds external to the test suite itself.

One way is to override the libc time functions using LD_PRELOAD using something like https://github.com/wolfcw/libfaketime This doesn't work with everything (for example doesn't work with Go because Go doesn't use libc for such things) but if it does then it's a very simple to use: % LD_PRELOAD=src/libfaketime.so.1 FAKETIME='1999-12-31 23:59:59' date Fri Dec 31 23:59:59 PST 1999 % LD_PRELOAD=src/libfaketime.so.1 FAKETIME='1999-12-31 23:59:59' python -c 'import time;print(time.ctime())' Fri Dec 31 23:59:59 1999 or to have the fake clock ticking starting from the specified time: % LD_PRELOAD=src/libfaketime.so.1 FAKETIME='@1999-12-31 23:59:59' python -c 'import time;print(time.ctime());time.sleep(1);print(time.ctime())' Fri Dec 31 23:59:59 1999 Sat Jan 1 00:00:00 2000

You don’t have to write that code yourself, you can just use libfaketime https://github.com/wolfcw/libfaketime

There's a well-known libfaketime library, that can forge the current system time. https://github.com/wolfcw/libfaketime Here's my friend's LD_PRELOAD hack, it pushes the idea further: hooking gettimeofday() to make a program to think that the time goes faster or slower. Useful for testing. https://github.com/m13253/clockslow

Interesting projects that employ LD_PRELOAD: https://github.com/stewartsmith/libeatmydata https://github.com/wolfcw/libfaketime https://cwrap.org/ https://github.com/dex4er/fakechroot https://blitiri.com.ar/p/libfiu/ https://github.com/paultag/tmperamental

It's worth mentioning that libfaketime [1] is a more mature alternative with macOS support and more complete coverage of the relevant system calls. Nothing against the current project but that might be a better choice for many people. [1] - https://github.com/wolfcw/libfaketime

You can use `libfaketime` to test your software: * https://github.com/wolfcw/libfaketime Shameless plug: my project `fluxcapacitor` may also be useful for testing: * https://github.com/majek/fluxcapacitor

See also libfaketime, which does all this and more besides: https://github.com/wolfcw/libfaketime