Opening a window from a test prevents libtest from outputting the test result

[dzfranklin]

Problem
If I spawn a window in a test I don't see the line test tests::foo ... ok. I know the test runs because it is included in the number of passed tests.

Steps

• Spawn a window in a test
• Run cargo test

Actual result:

running 2 tests
test tests::without_winit ... ok
   Doc-tests cargo_test_winit_repro

running 0 tests

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

Expected result:

running 2 tests
test tests::with_winit ... ok
test tests::without_winit ... ok
   Doc-tests cargo_test_winit_repro

running 0 tests

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

I've created a minimal crate that reproduces this issue.

Notes

Output of cargo version: cargo 1.52.0-nightly (90691f2bf 2021-03-16)
I've seen this result on Linux & Windows.

[ehuss]

Transferred to rust-lang/rust as this is an issue with libtest. libtest is the test harness which is responsible for running and reporting tests.

I don't have any specific ideas what could cause this. I imagine winit may be interfering somehow with stdout, though it is hard to say.

[ghost]

I think this is because EventLoop::run exits the process directly.

[dzfranklin]

That makes sense. I had assumed the same thread printed all the output lines. I suppose this is a wontfix then?

[Enselic]

Triage: let's close as duplicate to #67650 which is a about running each test in its own process, which in practice fixes this issue.