dylint

non_thread_safe_call_in_test

What it does

Checks for calls to non-thread-safe functions in code attributed with #[test]. For this lint to be effective, --tests must be passed to cargo check.

Why is this bad?

“When you run multiple tests, by default they run in parallel using threads” (reference). Calling a non-thread-safe function in one test could affect the outcome of another.

Known problems

• Synchronization is not considered, so false positives could result.
• Tries to flag uses of std::process::Command::new("cargo").arg("run"), but does not track values. So false negatives will result if the Command::new("cargo") is not Command::arg("run")’s receiver.

Example

#[test]
fn set_var() {
    std::env::set_var("KEY", "SOME_VALUE");
    std::process::Command::new("env").status().unwrap();
}

Use instead:

#[test]
fn set_var() {
    std::process::Command::new("env")
        .env("KEY", "SOME_VALUE")
        .status()
        .unwrap();
}

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