Proper "ignore test depending on env" handling

[crepererum]

Abstract

We want to skip tests if certain environment variables are NOT set (e.g. SOCKS_PROXY) so that developers do not need to provide a full-blown integration test infrastructure if they only work on a subset of the features.

ACs

• tests are skipped when environment variables are NOT set
• tests are skipped at runtime, NOT at compile time
• skipped tests are marked as "ignored"
• tests skipping requires little code (ideally a single line in form of a decorator, a function call, a macro call)

Current Situation

We currently use macros like this:

rskafka/tests/test_helpers.rs

Lines 75 to 93 in 6510b23

	/// Get the Socks Proxy environment variable.
	///
	/// If `SOCKS_PROXY` is not set, fail the tests and provide
	/// guidance for setting `SOCKS_PROXY`.
	#[macro_export]
	macro_rules! maybe_skip_SOCKS_PROXY {
	() => {{
	use std::env;
	dotenv::dotenv().ok();
	match (env::var("SOCKS_PROXY").ok()) {
	Some(proxy) => proxy,
	_ => {
	eprintln!("skipping integration tests with Proxy - set SOCKS_PROXY to run");
	return;
	}
	}
	}};
	}

This fulfills all ACs except for skipped tests are marked as "ignored".

References

• wip: socks 5 test #132 (comment)
• Add ability to ignore tests at runtime. rust-lang/rust#68007

[crepererum]

@mario-s volunteered to work on this 🎉