Add test process_spawned_outside_runtime

Signed-off-by: Jiahao XU <[email protected]>

tokio/tests/process_spawned_outside_runtime.rs

@@ -0,0 +1,24 @@
+#![cfg(feature = "process")]
+#![warn(rust_2018_idioms)]
+// This test reveals a difference in behavior of kqueue on FreeBSD. When the
+// reader disconnects, there does not seem to be an `EVFILT_WRITE` filter that
+// is returned.
+//
+// It is expected that `EVFILT_WRITE` would be returned with either the
+// `EV_EOF` or `EV_ERROR` flag set. If either flag is set a write would be
+// attempted, but that does not seem to occur.
+#![cfg(all(unix, not(target_os = "freebsd")))]
+
+use std::process::Stdio;
+use tokio::process::Command;
+
+#[test]
+#[should_panic(
+    expected = "there is no reactor running, must be called from the context of a Tokio 1.x runtime"
+)]
+fn process_spawned_outside_runtime() {
+    let _ = Command::new("true")
+        .stdin(Stdio::piped())
+        .stdout(Stdio::null())
+        .spawn();
+}