write the remaining test fake executables from a child process

hive-runtime/src/stop.rs

@@ -64,6 +64,24 @@ mod tests {
         sleep 30 >/dev/null 2>&1 &\n\
         wait\n";
 
+    /// Write the script `body` to `path` as an executable, from a child process
+    /// rather than from this one: a write fd on it held here could be inherited
+    /// by a child another test thread forks, and exec'ing a file some process
+    /// still holds open for writing fails with `ETXTBSY`.
+    fn write_executable(path: &Path, body: &str) {
+        let status = std::process::Command::new("/bin/sh")
+            .args([
+                "-c",
+                r#"printf '%s' "$1" > "$2" && chmod 755 "$2""#,
+                "sh",
+                body,
+            ])
+            .arg(path)
+            .status()
+            .expect("run /bin/sh");
+        assert!(status.success(), "writing {} failed", path.display());
+    }
+
     async fn exists(path: &Path) {
         for _ in 0..250 {
             if path.exists() {
@@ -76,12 +94,9 @@ mod tests {
 
     #[tokio::test]
     async fn a_claude_stop_is_a_sigint_to_the_process() {
-        use std::os::unix::fs::PermissionsExt as _;
-
         let dir = tempfile::tempdir().unwrap();
         let program = dir.path().join("fake-claude");
-        std::fs::write(&program, FAKE_CLAUDE).unwrap();
-        std::fs::set_permissions(&program, std::fs::Permissions::from_mode(0o755)).unwrap();
+        write_executable(&program, FAKE_CLAUDE);
         let (ready, mark) = (dir.path().join("ready"), dir.path().join("int"));
         let config = Config {
             program: Some(program),