Need an option to prevent cargo test from initializing logging

[dfoxfranke]

I'm trying to unit test program functionality that reopens log files on receiving a SIGHUP. My unit test does this:

        let tempdir = tempfile::TempDir::new().unwrap();
        let mut logpath = path::PathBuf::from(tempdir.path());
        let mut logpath_rotated = logpath.clone();
        logpath.push("logfile");
        logpath_rotated.push("logfile.old");
        let logconfig = vec![LogConfig::FileLog(logpath.clone(), log::LevelFilter::Info)];
        let handle = init_logging(&logconfig).unwrap();
        info!("PRE-ROTATION");
        fs::rename(&logpath, &logpath_rotated).unwrap();
        info!("MID-ROTATION");
        reinit_logging(&logconfig, &handle).unwrap();
        info!("POST-ROTATION");

My init_logging and reinit_logging functions call into my log provider, which is log4rs. After running the above code, I'd be rereading "logfile" to make sure it contains the "POST-ROTATION" message, and "logfile.old" to make sure it contains the "PRE-ROTATION" and "MID-ROTATION" messages.

Problem is, it doesn't work, because it panics on init_logging(&logconfig).unwrap(). log4rs is calling log::set_logger and getting back a SetLoggerError, because cargo test has already initialized before it ever calls into my test.

There seems to be no way around this without abandoning the cargo test framework altogether, since as of 0.4 the log crate no longer provides any mechanism for de-initializing logging. I'd like to be able to add some attribute like #[test_no_init_logging] to my unit test to tell cargo "don't touch".

[ehuss]

This is an inherent limitation of multi-threaded tests and using a global system like the log crate.

I don't offhand have any great suggestions for you. Some random things:

• Set up a test without a harness, and write your own main function.
• Use a non-global logging framework.
• Perhaps in the future the test framework can support process-per-test via panic=abort testing / subprocess testing rust#67650. This is implemented for abort panic crates, but could be generalized for other cases like this.
• Perhaps in the future custom test frameworks could make it easier.

The first option above would probably be the easiest. You might want to follow up on one of the user forums to see if anyone has better ideas.

I'm going to close this since it isn't a Cargo issue. The test framework which handles tests (libtest) lives in https://github.com/rust-lang/rust/.