Test that an added printer joins the fleet and survives a restart

The OctoPrint client's connect succeeds without hardware, so it stands in
to prove the plumbing of a successful add: saved, joins the running fleet,
refused when added twice, and rebuilt from the store after a restart.

src/provision.rs

@@ -201,6 +201,38 @@ mod behaviour {
         let _ = std::fs::remove_file(path);
     }
 
+    /// The success path, using the OctoPrint client because its `connect` is
+    /// the one that succeeds without a real machine (the driver is a stub).
+    /// What this proves is the plumbing, not a vendor: a connected printer is
+    /// saved, joins the running fleet, and is still there after a "restart"
+    /// that reopens the store and rebuilds the fleet from it.
+    #[tokio::test]
+    async fn an_added_printer_joins_the_fleet_and_survives_a_restart() {
+        let (store, path) = store();
+        let fleet = empty_fleet();
+        let mut req = request("octo1");
+        req.vendor = "octoprint".into();
+        req.sn = None;
+        req.access_code = None;
+        req.api_key = Some("key-123".into());
+
+        add(&fleet, &store, req.clone()).await.unwrap();
+        assert!(fleet.lock().await.iter().any(|p| p.base().id == "octo1"));
+
+        // Same id again: refused, and the first is untouched.
+        let again = add(&fleet, &store, req).await.unwrap_err();
+        assert!(again.contains("already has"), "{again}");
+        assert_eq!(fleet.lock().await.len(), 1);
+
+        // "Restart": reopen the store, rebuild what main would.
+        drop(store);
+        let reopened = Store::open(&path).unwrap();
+        let rebuilt: Vec<_> = reopened.printers().unwrap().into_iter().map(|e| crate::fleet::build(e).unwrap()).collect();
+        assert_eq!(rebuilt.len(), 1);
+        assert_eq!(rebuilt[0].base().id, "octo1");
+        let _ = std::fs::remove_file(path);
+    }
+
     #[test]
     fn the_wire_message_parses_and_its_debug_hides_the_credential() {
         let json = r#"{"type":"provision_printer","request_id":"r1","printer":{"id":"p1","name":"Bench","vendor":"bambu","host":"10.0.0.5","access_code":"98765432","sn":"SN1"}}"#;