Explain active Domain maintenance contention

crates/lazaret-client/tests/state_cli.rs

@@ -1,5 +1,7 @@
 use std::fs;
 
+use lazaret_linux::filesystem::try_exclusive_flock;
+
 #[allow(clippy::disallowed_methods, clippy::disallowed_types)]
 #[test]
 fn machine_and_human_discovery_are_versioned_and_content_free() {
@@ -42,6 +44,35 @@ fn reset_refuses_an_arbitrary_container_or_host_path_before_state_access() {
     );
 }
 
+#[allow(clippy::disallowed_methods, clippy::disallowed_types)]
+#[test]
+fn active_domain_reports_actionable_maintenance_contention() {
+    let fixture = Fixture::new();
+    assert!(fixture.command("list").output().unwrap().status.success());
+    let lock = try_exclusive_flock(
+        fs::OpenOptions::new()
+            .read(true)
+            .write(true)
+            .open(fixture.domain_root().join("domain.lock"))
+            .unwrap(),
+    )
+    .unwrap();
+
+    let active = fixture.command("verify").output().unwrap();
+    assert!(!active.status.success());
+    assert!(String::from_utf8_lossy(&active.stderr).contains(
+        "Domain state is busy; exit active Lazaret sessions or wait for another maintenance command to finish, then retry"
+    ));
+
+    drop(lock);
+    let inactive = fixture.command("verify").output().unwrap();
+    assert!(
+        inactive.status.success(),
+        "{}",
+        String::from_utf8_lossy(&inactive.stderr)
+    );
+}
+
 #[allow(clippy::disallowed_methods, clippy::disallowed_types)]
 #[test]
 fn missing_store_succeeds_only_when_the_complete_state_anchor_is_absent() {