$ rustc -vV
rustc 1.90.0 (1159e78c4 2025-09-14) (built from a source tarball)
binary: rustc
commit-hash: 1159e78c4747b02ef996e55082b704c09b970588
commit-date: 2025-09-14
host: x86_64-unknown-openbsd
release: 1.90.0
LLVM version: 19.1.7

$ cargo test -v --no-default-features --features stdbuf
(...)
running 6 tests
test test_stdbuf::invalid_input ... ok
test test_stdbuf::test_no_such ... ok
test test_stdbuf::test_permission ... ok
test test_stdbuf::test_stdbuf_line_buffering_stdin_fails ... ok
test test_stdbuf::test_stdbuf_no_buffer_option_fails ... ok
test test_stdbuf::test_stdbuf_invalid_mode_fails ... ok

test result: ok. 6 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.12s