Crate fault_injection

Macros

annotate
Annotates an io::Error with the crate, file, and line number where the annotation has been performed.
fallible
Similar to the try! macro or ? operator, but externally controllable to inject faults during testing. Unlike the try! macro or ? operator, this additionally annotates the description of the error to include the crate, file name, and line number where the error originated from to facilitate quick debugging. It is specialized to work with io::Result types, and will return an io::Error for faults, with into() called similar to the try! macro or ? operator. Decrements the FAULT_INJECT_COUNTER by 1 (it is set to u64::MAX by default), and if it hits 0, returns an io::Error with a kind of Other. If SLEEPINESS is set to something other than 0, this macro will also inject weakly pseudorandom delays for facilitating a basic form of concurrency testing.
maybe
Performs the same fault injection as fallible but does not early-return, and does not try to convert the injected io::Error using the ? operator.

FAULT_INJECT_COUNTER
Facilitates fault injection. Every time any IO operation is performed, this is decremented. If it hits 0, an io::Error is returned from that IO operation. Use this to ensure that error handling is being performed, by running some test workload, checking the counter, and then setting this to an incrementally-lower number while asserting that your application properly handles the error that will propagate up. Defaults to u64::MAX, so it won’t be hit normally unless you do something 6 billion times per second for 100 years. If you’re building something like that, maybe consider re-setting this to u64::MAX every few decades for safety.
SLEEPINESS
Facilitates delay injection. If you set this to something other than 0, the fallible! macro will randomly call std::thread::yield_now(), with the nubmer of times being multiplied by this value. You should not need to set it very high to get a lot of delays, but you’ll need to play with the number sometimes for specific concurrent systems under test.

set_trigger_function
This function will be called any time the FAULT_INJECT_COUNTER reaches 0 and an error is injected. You can use this to re-set the counter for deep fault tree enumeration, test auditing, etc…