T04: own Unix pty so a failed chdir fails the start; closing logs and reaps

src/testlog.rs

@@ -0,0 +1,36 @@
+use std::sync::{Mutex, Once};
+
+static LINES: Mutex<Vec<String>> = Mutex::new(Vec::new());
+
+/// Keeps every log line so tests can assert what was logged.
+struct Capture;
+
+impl log::Log for Capture {
+    fn enabled(&self, metadata: &log::Metadata) -> bool {
+        metadata.level() <= log::Level::Debug
+    }
+
+    fn log(&self, record: &log::Record) {
+        let line = record.args().to_string();
+        eprintln!("{} {line}", record.level());
+        LINES.lock().expect("the log lines").push(line);
+    }
+
+    fn flush(&self) {}
+}
+
+pub fn init() {
+    static ONCE: Once = Once::new();
+    ONCE.call_once(|| {
+        log::set_logger(&Capture).expect("the only logger in tests");
+        log::set_max_level(log::LevelFilter::Debug);
+    });
+}
+
+pub fn logged(line: &str) -> bool {
+    LINES
+        .lock()
+        .expect("the log lines")
+        .iter()
+        .any(|kept| kept == line)
+}