Injected fake is called outside of scope sporadically

[schaffenrath]

In some cases, an injected fake is called outside the scope (test) it was defined in.

Test scenario

With the following simple structure:

.
├── main.rs
└── test_module
    ├── first.rs
    ├── mod.rs
    └── second.rs

and first.rs:

pub struct First {
    a: i32,
}

impl First {
    pub fn new() -> Self {
        First { a: 0 }
    }

    pub fn get(&self) -> i32 {
        self.a
    }
}

#[cfg(test)]
mod tests {
    use injectorpp::interface::injector::*;

    use crate::test_module::first::First;

    #[test]
    fn get_call_mock() {
        let mut injector = InjectorPP::new();
        injector
            .when_called(injectorpp::func!(fn (First::get)(&First) -> i32))
            .will_execute(injectorpp::fake!(func_type: fn(_i: &First)-> i32, returns: 7));

        assert_eq!(First::new().get(), 7);
    }
}

and second.rs:

use super::first::First;

pub struct Second {
    tm: First,
}

impl Second {
    pub fn new() -> Self {
        Second { tm: First::new() }
    }

    pub fn get(&self) -> i32 {
        self.tm.get()
    }
}

#[cfg(test)]
mod tests {
    use super::Second;

    #[test]
    fn get_do_not_call_mock() {
        assert_eq!(Second::new().get(), 0);
    }
}

Expected behavior

The .get() method in the test of second.rs should always return 0, since the new() initialized it that way, and the injected fake should only be valid in the test of first.rs.

Actual behavior

Running cargo test many times:

for i in $(seq 0 300); do cargo test; done

the following issue might occur:

running 2 tests
test test_module::first::tests::get_call_mock ... ok
test test_module::second::tests::get_do_not_call_mock ... FAILED

failures:

---- test_module::second::tests::get_do_not_call_mock stdout ----

thread 'test_module::second::tests::get_do_not_call_mock' panicked at src/test_module/second.rs:23:9:
assertion `left == right` failed
  left: 7
 right: 0
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace


failures:
    test_module::second::tests::get_do_not_call_mock

test result: FAILED. 1 passed; 1 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s

[mazong1123]

Thanks for reporting this. This is a known issue and we are trying to fix it. cargo test by default runs test cases in multi-thread. The function First::get could be faked while Second::new().get() is executing. The problem is there's only 1 copy of First::get per process. So changing the First::get in first.rs thread will impact the second.rs thread.

There're several workaround options before this bug is fixed:

• Option 1: add an injectorpp instance at the beginning of get_do_not_call_mock even if there's no need to mock. This can prevent the threading issue as injectorpp needs to acquire a lock: let _injector = InjectorPP::new();
• Option 2: use cargo-nextest as the test runner. It runs the test cases in different processes.
• Option 3: use cargo test -- --test-threads=1.

[ffguven]

I hit the same issue when

• test_1 in test_module_1 mocks a private function within the parent module
• test_2 in test_module_1 tries to use that private function right away without mocking it.

test_2's function call is basically returning the mock error I introduced within the test_1.

It works good when just hitting cargo test, but fails consistently when I try to execute the tests via cargo tarpaulin --out Xml on Github Actions VM.

Creating a dummy InjectorPP instance at the beginning of test_2 helped as a workaround.