AI masters build only rooms and towers they have researched

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/rival.rs

@@ -600,6 +600,37 @@ mod tests {
         g
     }
 
+    #[test]
+    fn the_ai_partner_builds_only_what_is_researched() {
+        // the first missions of both co-op campaigns: no library, no forge yet
+        let doc = crate::editor::coop_campaign::coop_campaign();
+        let games = [
+            crate::campaign::start_editor_coop_mission(&doc.missions[0], 0, 77),
+            crate::campaign::start_coop_mission(crate::campaign::coop_mission_indexes()[0], None),
+        ];
+        let lib = crate::ui::TOOLS.iter().position(|&t| t == crate::ui::Tool::Room(4)).unwrap();
+        let forge = crate::ui::TOOLS.iter().position(|&t| t == crate::ui::Tool::Room(8)).unwrap();
+        for mut g in games {
+            g.coop = true;
+            assert!(g.start_match(&[0, 2], 0));
+            g.sync_ai_sides(&[2], 1);
+            g.end_match();
+            let mine_knows = (g.tool_allowed(lib), g.tool_allowed(forge));
+            for _ in 0..(10 * 60 * 20) {
+                g.update(0.05);
+            }
+            let owner = Owner::of_side(2);
+            let has = |k: Kind| g.map.t.iter().any(|t| t.kind == k && t.owner == owner);
+            if !mine_knows.0 {
+                assert!(!has(Kind::Library), "the partner has no library either");
+            }
+            if !mine_knows.1 {
+                assert!(!has(Kind::Forge), "the partner has no forge either");
+            }
+            assert!(has(Kind::Lair) || has(Kind::Treasury), "but builds what it knows");
+        }
+    }
+
     #[test]
     fn imps_take_ground_from_enemies_but_never_from_allies() {
         let mut g = offline_league_game();