write the review-classifier fake agent scripts from a child process

swarm-review-classifier/src/test_script.rs

@@ -0,0 +1,25 @@
+//! Fake agent scripts for the tests.
+
+use std::path::Path;
+
+/// 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`.
+///
+/// # Panics
+///
+/// If `/bin/sh` cannot run or the write fails.
+pub 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());
+}