fix(tyrant): synchronize rejected captured-mob transfers

src/main/java/games/dmg/spigottyrant/CapturedMobInventoryService.java

@@ -31,6 +31,19 @@ public final class CapturedMobInventoryService {
             }
         }
         Set<UUID> retained = new HashSet<>();
+        ItemStack cursor = player.getItemOnCursor();
+        if (items.isCapturedMob(cursor)) {
+            UUID captureId = items.captureId(cursor).orElseThrow();
+            if (items.owner(cursor).filter(state.playerId()::equals).isPresent()
+                    && stored.containsKey(captureId) && retained.add(captureId)) {
+                if (cursor.getAmount() > 1) {
+                    cursor.setAmount(1);
+                    player.setItemOnCursor(cursor);
+                }
+            } else {
+                player.setItemOnCursor(null);
+            }
+        }
         ItemStack[] contents = player.getInventory().getContents();
         for (int index = 0; index < contents.length; index++) {
             ItemStack item = contents[index];
@@ -42,6 +55,9 @@ public final class CapturedMobInventoryService {
                 && stored.containsKey(captureId) && retained.add(captureId);
             if (!valid) {
                 player.getInventory().setItem(index, null);
+            } else if (item.getAmount() > 1) {
+                item.setAmount(1);
+                player.getInventory().setItem(index, item);
             }
         }
         for (Map.Entry<UUID, CapturedMob> entry : stored.entrySet()) {

src/main/java/games/dmg/spigottyrant/SpigotTyrantPlugin.java

@@ -205,7 +205,7 @@ public final class SpigotTyrantPlugin extends JavaPlugin {
         getServer().getPluginManager().registerEvents(
             new TamerListener(
                 stateManager, abilityItems, capturedMobItems, capturedMobs,
-                settings, getServer()
+                settings, getServer(), task -> getServer().getScheduler().runTask(this, task)
             ),
             this
         );

src/main/java/games/dmg/spigottyrant/TamerListener.java

@@ -33,6 +33,8 @@ public final class TamerListener implements Listener {
     private final CapturedMobService capturedMobs;
     private final PluginSettings settings;
     private final Server server;
+    private final java.util.function.Consumer<Runnable> nextTick;
+    private final java.util.Set<UUID> pendingInventoryRefresh = new java.util.HashSet<>();
 
     public TamerListener(
         TyrantStateManager stateManager,
@@ -40,7 +42,8 @@ public final class TamerListener implements Listener {
         CapturedMobItemService capturedItems,
         CapturedMobService capturedMobs,
         PluginSettings settings,
-        Server server
+        Server server,
+        java.util.function.Consumer<Runnable> nextTick
     ) {
         this.stateManager = stateManager;
         this.abilityItems = abilityItems;
@@ -48,6 +51,7 @@ public final class TamerListener implements Listener {
         this.capturedMobs = capturedMobs;
         this.settings = settings;
         this.server = server;
+        this.nextTick = nextTick;
     }
 
     @EventHandler(priority = EventPriority.HIGH)
@@ -162,15 +166,82 @@ public final class TamerListener implements Listener {
 
     @EventHandler
     public void onInventoryClick(InventoryClickEvent event) {
-        if (capturedItems.isCapturedMob(event.getCurrentItem())
-                || capturedItems.isCapturedMob(event.getCursor())) {
-            if (!(event.getWhoClicked() instanceof Player player)
-                    || event.isShiftClick()
-                    || event.getClickedInventory() == null
-                    || !event.getClickedInventory().equals(player.getInventory())) {
-                event.setCancelled(true);
+        Player player = event.getWhoClicked() instanceof Player clicked ? clicked : null;
+        ItemStack swapSource = null;
+        if (player != null) {
+            if (event.getHotbarButton() >= 0 && event.getHotbarButton() < 9) {
+                swapSource = player.getInventory().getItem(event.getHotbarButton());
+            } else if (event.getClick() == org.bukkit.event.inventory.ClickType.SWAP_OFFHAND) {
+                swapSource = player.getInventory().getItemInOffHand();
             }
         }
+        if (capturedItems.isCapturedMob(event.getCurrentItem())
+                || capturedItems.isCapturedMob(event.getCursor()) || capturedItems.isCapturedMob(swapSource)) {
+            var action = event.getAction();
+            if (player == null || event.isCancelled() || event.isShiftClick()
+                    || action == org.bukkit.event.inventory.InventoryAction.MOVE_TO_OTHER_INVENTORY
+                    || action == org.bukkit.event.inventory.InventoryAction.CLONE_STACK
+                    || action == org.bukkit.event.inventory.InventoryAction.COLLECT_TO_CURSOR
+                    || action == org.bukkit.event.inventory.InventoryAction.UNKNOWN
+                    || event.getClickedInventory() == null
+                    || !event.getClickedInventory().equals(player.getInventory())
+                    || !ownedBy(player, event.getCurrentItem()) || !ownedBy(player, event.getCursor())
+                    || !ownedBy(player, swapSource)) {
+                event.setCancelled(true);
+                if (player != null) {
+                    refreshInventory(player);
+                }
+            }
+        }
+    }
+
+    @EventHandler
+    public void onInventoryDrag(org.bukkit.event.inventory.InventoryDragEvent event) {
+        if (!capturedItems.isCapturedMob(event.getOldCursor())
+                && event.getNewItems().values().stream().noneMatch(capturedItems::isCapturedMob)) {
+            return;
+        }
+        Player player = event.getWhoClicked() instanceof Player dragged ? dragged : null;
+        if (player == null || event.isCancelled() || !ownedBy(player, event.getOldCursor())
+                || event.getNewItems().values().stream().anyMatch(item -> !ownedBy(player, item))
+                || event.getRawSlots().stream().anyMatch(raw ->
+                    !player.getInventory().equals(event.getView().getInventory(raw)))) {
+            event.setCancelled(true);
+            if (player != null) {
+                refreshInventory(player);
+            }
+        }
+    }
+
+    @EventHandler
+    public void onInventoryMove(org.bukkit.event.inventory.InventoryMoveItemEvent event) {
+        if (capturedItems.isCapturedMob(event.getItem())) {
+            event.setCancelled(true);
+        }
+    }
+
+    private boolean ownedBy(Player player, ItemStack item) {
+        return !capturedItems.isCapturedMob(item)
+            || capturedItems.owner(item).filter(player.getUniqueId()::equals).isPresent();
+    }
+
+    private void refreshInventory(Player player) {
+        UUID id = player.getUniqueId();
+        if (!pendingInventoryRefresh.add(id)) {
+            return;
+        }
+        // The native click transaction must finish before forcing its authoritative contents to the client.
+        try {
+            nextTick.accept(() -> {
+                pendingInventoryRefresh.remove(id);
+                if (player.isOnline()) {
+                    player.updateInventory();
+                }
+            });
+        } catch (RuntimeException exception) {
+            pendingInventoryRefresh.remove(id);
+            throw exception;
+        }
     }
 
     @EventHandler

src/test/java/games/dmg/spigottyrant/CapturedMobInventorySynchronizationTest.java

@@ -0,0 +1,358 @@
+package games.dmg.spigottyrant;
+
+import static org.junit.jupiter.api.Assertions.*;
+import static org.mockito.Mockito.*;
+
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+import java.util.Set;
+import java.util.UUID;
+import java.util.concurrent.atomic.AtomicReference;
+import java.util.logging.Logger;
+import org.bukkit.NamespacedKey;
+import org.bukkit.Server;
+import org.bukkit.entity.Player;
+import org.bukkit.event.inventory.ClickType;
+import org.bukkit.event.inventory.InventoryAction;
+import org.bukkit.event.inventory.InventoryClickEvent;
+import org.bukkit.event.inventory.InventoryType;
+import org.bukkit.inventory.Inventory;
+import org.bukkit.inventory.InventoryView;
+import org.bukkit.inventory.ItemStack;
+import org.bukkit.inventory.PlayerInventory;
+import org.bukkit.inventory.meta.ItemMeta;
+import org.bukkit.persistence.PersistentDataContainer;
+import org.bukkit.persistence.PersistentDataType;
+import org.bukkit.plugin.Plugin;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.io.TempDir;
+
+class CapturedMobInventorySynchronizationTest {
+    @TempDir Path directory;
+    private final UUID owner = UUID.randomUUID(), captureId = UUID.randomUUID();
+    private final Player player = mock(Player.class);
+    private final PlayerInventory inventory = mock(PlayerInventory.class);
+    private final Inventory top = mock(Inventory.class);
+    private final InventoryView view = mock(InventoryView.class);
+    private final Server server = mock(Server.class);
+    private final ItemStack[] contents = new ItemStack[41];
+    private final AtomicReference<ItemStack> cursor = new AtomicReference<>();
+    private final List<Runnable> scheduled = new ArrayList<>();
+    private TyrantStateManager manager;
+    private CapturedMobItemService items;
+    private TamerListener listener;
+    private ItemStack egg;
+    private Path stateFile;
+
+    @BeforeEach
+    void setup() throws Exception {
+        when(player.getUniqueId()).thenReturn(owner);
+        when(player.getName()).thenReturn("Tamer");
+        when(player.isOnline()).thenReturn(true);
+        when(player.getInventory()).thenReturn(inventory);
+        when(player.getItemOnCursor()).thenAnswer(call -> cursor.get());
+        doAnswer(call -> { cursor.set(call.getArgument(0)); return null; })
+            .when(player).setItemOnCursor(nullable(ItemStack.class));
+        when(inventory.getContents()).thenAnswer(call -> contents.clone());
+        when(inventory.getItem(anyInt())).thenAnswer(call -> contents[call.getArgument(0, Integer.class)]);
+        doAnswer(call -> { contents[call.getArgument(0, Integer.class)] = call.getArgument(1); return null; })
+            .when(inventory).setItem(anyInt(), nullable(ItemStack.class));
+        when(view.getPlayer()).thenReturn(player);
+        when(view.getBottomInventory()).thenReturn(inventory);
+        when(view.getTopInventory()).thenReturn(top);
+        when(top.getSize()).thenReturn(27);
+        when(top.getContents()).thenReturn(new ItemStack[27]);
+        when(view.getInventory(anyInt())).thenAnswer(call -> {
+            int raw = call.getArgument(0);
+            return raw < 0 || raw >= 68 ? null : raw < 27 ? top : inventory;
+        });
+        when(view.convertSlot(anyInt())).thenAnswer(call -> call.getArgument(0, Integer.class) - 27);
+        when(view.getItem(anyInt())).thenAnswer(call -> {
+            int raw = call.getArgument(0);
+            return raw >= 27 && raw < 68 ? contents[raw - 27] : null;
+        });
+        when(view.getCursor()).thenAnswer(call -> cursor.get());
+        Plugin plugin = mock(Plugin.class);
+        when(plugin.getName()).thenReturn("SpigotTyrant");
+        items = new BukkitCapturedMobItemService(plugin, PluginSettings.from(Map.of()));
+        egg = egg(owner, captureId);
+        contents[3] = egg;
+        stateFile = directory.resolve("state.yml");
+        manager = new TyrantStateManager(new YamlTyrantStateRepository(stateFile), Logger.getAnonymousLogger());
+        var mob = new CapturedMob("COW", Map.of("capture-id", captureId.toString(), "snapshot", "stored-cow"));
+        var state = new PlayerState(owner, "Tamer", Optional.empty(), Optional.empty(), TyrantClass.TAMER,
+            Optional.empty(), Map.of(), Set.of(), List.of(mob));
+        manager.updatePlayer(owner, "Tamer", ignored -> state);
+        assertTrue(manager.saveIfDirty());
+        listener = new TamerListener(manager, mock(AbilityItemService.class), items,
+            new CapturedMobService(), PluginSettings.from(Map.of()), server, scheduled::add);
+    }
+
+    @Test
+    void rejectedShiftKeepsAuthoritativeEggAndCustodyAndResendsAfterTransaction() throws Exception {
+        var before = manager.snapshot();
+        byte[] bytes = Files.readAllBytes(stateFile);
+        var event = click(30, ClickType.SHIFT_LEFT, InventoryAction.MOVE_TO_OTHER_INVENTORY, -1);
+        listener.onInventoryClick(event);
+        assertTrue(event.isCancelled());
+        assertSame(egg, contents[3]);
+        assertTrue(java.util.Arrays.stream(top.getContents()).allMatch(java.util.Objects::isNull));
+        verify(player, never()).updateInventory();
+        assertEquals(1, scheduled.size(), "A rejected transfer needs a post-transaction full inventory refresh");
+        scheduled.remove(0).run();
+        verify(player).updateInventory();
+        assertEquals(before, manager.snapshot());
+        assertArrayEquals(bytes, Files.readAllBytes(stateFile));
+        assertEquals(1, new YamlTyrantStateRepository(stateFile).load().players().get(owner).capturedMobs().size());
+        verify(server, never()).getEntityFactory();
+        verify(inventory, never()).setItem(anyInt(), nullable(ItemStack.class));
+    }
+
+    @Test
+    void repeatedRejectedTransfersCoalesceRefreshWithoutChangingEggOrCustody() throws Exception {
+        var before = manager.snapshot();
+        byte[] bytes = Files.readAllBytes(stateFile);
+        for (int tick = 0; tick < 3; tick++) {
+            for (int attempt = 0; attempt < 5; attempt++) {
+                var event = click(30, ClickType.SHIFT_LEFT, InventoryAction.MOVE_TO_OTHER_INVENTORY, -1);
+                listener.onInventoryClick(event);
+                assertTrue(event.isCancelled());
+                assertSame(egg, contents[3]);
+            }
+            assertEquals(1, scheduled.size(), "Repeated rejects in one tick need one authoritative refresh");
+            scheduled.remove(0).run();
+        }
+        verify(player, times(3)).updateInventory();
+        assertEquals(before, manager.snapshot());
+        assertArrayEquals(bytes, Files.readAllBytes(stateFile));
+        assertEquals(1, egg.getAmount());
+        assertTrue(java.util.Arrays.stream(top.getContents()).allMatch(java.util.Objects::isNull));
+    }
+
+    @Test
+    void logoutBeforeRefreshDoesNotMutateOrReissueAnything() {
+        var before = manager.snapshot();
+        listener.onInventoryClick(click(30, ClickType.SHIFT_LEFT, InventoryAction.MOVE_TO_OTHER_INVENTORY, -1));
+        when(player.isOnline()).thenReturn(false);
+        scheduled.remove(0).run();
+        verify(player, never()).updateInventory();
+        assertSame(egg, contents[3]);
+        assertEquals(before, manager.snapshot());
+    }
+
+    @Test
+    void rejectedSchedulingDoesNotPermanentlySuppressLaterRefresh() {
+        int[] attempts = {0};
+        listener = new TamerListener(manager, mock(AbilityItemService.class), items,
+            new CapturedMobService(), PluginSettings.from(Map.of()), server, task -> {
+                if (attempts[0]++ == 0) { throw new IllegalStateException("scheduler unavailable"); }
+                scheduled.add(task);
+            });
+        var first = click(30, ClickType.SHIFT_LEFT, InventoryAction.MOVE_TO_OTHER_INVENTORY, -1);
+        assertThrows(IllegalStateException.class, () -> listener.onInventoryClick(first));
+        assertTrue(first.isCancelled());
+        listener.onInventoryClick(click(30, ClickType.SHIFT_LEFT, InventoryAction.MOVE_TO_OTHER_INVENTORY, -1));
+        assertEquals(1, scheduled.size());
+        scheduled.remove(0).run();
+        verify(player).updateInventory();
+    }
+
+    @Test
+    void recoveryDoesNotDuplicateAnEggHeldOnTheCursor() {
+        contents[3] = null;
+        cursor.set(egg);
+        when(inventory.addItem(any(ItemStack[].class))).thenAnswer(call -> {
+            ItemStack[] added = (ItemStack[]) call.getRawArguments()[0];
+            for (ItemStack item : added) {
+                for (int index = 0; index < contents.length; index++) {
+                    if (contents[index] == null) { contents[index] = item; break; }
+                }
+            }
+            return new java.util.HashMap<Integer, ItemStack>();
+        });
+        var before = manager.snapshot();
+        var recovery = new CapturedMobInventoryService(items, PluginSettings.from(Map.of()));
+        try (var constructed = mockConstruction(ItemStack.class, (item, context) -> markEgg(item, owner, captureId))) {
+            for (int attempt = 0; attempt < 3; attempt++) {
+                recovery.reconcile(player, manager.player(owner, "Tamer"));
+            }
+            assertEquals(0, constructed.constructed().size(), "Cursor-held egg already represents the stored mob");
+            assertTrue(java.util.Arrays.stream(contents).allMatch(java.util.Objects::isNull));
+            assertSame(egg, cursor.get());
+            assertEquals(before, manager.snapshot());
+        }
+    }
+
+    @Test
+    void reconciliationKeepsCursorCopyAndRemovesOnlyDuplicateEggs() {
+        cursor.set(egg);
+        egg.setAmount(2);
+        contents[3] = egg(owner, captureId);
+        ItemStack ordinary = mock(ItemStack.class);
+        contents[4] = ordinary;
+        var before = manager.snapshot();
+        new CapturedMobInventoryService(items, PluginSettings.from(Map.of()))
+            .reconcile(player, manager.player(owner, "Tamer"));
+        assertSame(egg, cursor.get());
+        assertEquals(1, egg.getAmount());
+        assertNull(contents[3]);
+        assertSame(ordinary, contents[4]);
+        assertEquals(before, manager.snapshot());
+    }
+
+    @Test
+    void cursorEggIsRemovedOnlyWhenCustodyIsGoneOrOwnershipIsInvalid() {
+        contents[3] = null;
+        cursor.set(egg);
+        var released = new CapturedMobService().release(manager.player(owner, "Tamer"), captureId);
+        var recovery = new CapturedMobInventoryService(items, PluginSettings.from(Map.of()));
+        recovery.reconcile(player, released);
+        assertNull(cursor.get(), "A released mob must not leave a cursor token behind");
+        contents[3] = egg;
+        cursor.set(egg(UUID.randomUUID(), captureId));
+        recovery.reconcile(player, manager.player(owner, "Tamer"));
+        assertNull(cursor.get(), "Foreign items cannot be retained");
+        assertSame(egg, contents[3]);
+    }
+
+    @Test
+    void hiddenHotbarTransferIsRejectedAndResynchronized() {
+        contents[3] = null;
+        contents[2] = egg;
+        var event = click(0, ClickType.NUMBER_KEY, InventoryAction.HOTBAR_SWAP, 2);
+        listener.onInventoryClick(event);
+        assertTrue(event.isCancelled());
+        assertEquals(1, scheduled.size());
+        scheduled.remove(0).run();
+        verify(player).updateInventory();
+        assertSame(egg, contents[2]);
+    }
+
+    @Test
+    void hiddenOffhandTransferIsRejectedAndResynchronized() {
+        contents[3] = null;
+        contents[40] = egg;
+        when(inventory.getItemInOffHand()).thenReturn(egg);
+        var event = click(0, ClickType.SWAP_OFFHAND, InventoryAction.HOTBAR_SWAP, -1);
+        listener.onInventoryClick(event);
+        assertTrue(event.isCancelled());
+        assertEquals(1, scheduled.size());
+    }
+
+    @Test
+    void crossInventoryDragIsRejectedAndResynchronized() {
+        cursor.set(egg);
+        contents[3] = null;
+        var event = new org.bukkit.event.inventory.InventoryDragEvent(view, null, egg, false, Map.of(0, egg, 30, egg));
+        listener.onInventoryDrag(event);
+        assertTrue(event.isCancelled());
+        assertEquals(1, scheduled.size());
+        assertSame(egg, cursor.get());
+    }
+
+    @Test
+    void automatedTransferCannotMoveCapturedEggs() {
+        var hopper = new org.bukkit.event.inventory.InventoryMoveItemEvent(top, egg, mock(Inventory.class), true);
+        listener.onInventoryMove(hopper);
+        assertTrue(hopper.isCancelled());
+        assertTrue(scheduled.isEmpty(), "Automated moves have no predicting player to refresh");
+    }
+
+    @Test
+    void cloningCannotCreateAdditionalEggCopies() {
+        var clone = click(30, ClickType.MIDDLE, InventoryAction.CLONE_STACK, -1);
+        listener.onInventoryClick(clone);
+        assertTrue(clone.isCancelled());
+        assertEquals(1, scheduled.size());
+    }
+
+    @Test
+    void ordinaryItemsRemainUnaffectedWithoutRefreshTraffic() {
+        ItemStack ordinary = mock(ItemStack.class);
+        when(ordinary.clone()).thenReturn(ordinary);
+        contents[3] = ordinary;
+        var shift = click(30, ClickType.SHIFT_LEFT, InventoryAction.MOVE_TO_OTHER_INVENTORY, -1);
+        listener.onInventoryClick(shift);
+        assertFalse(shift.isCancelled());
+        var drag = new org.bukkit.event.inventory.InventoryDragEvent(view, null, ordinary, false, Map.of(0, ordinary));
+        listener.onInventoryDrag(drag);
+        assertFalse(drag.isCancelled());
+        var hopper = new org.bukkit.event.inventory.InventoryMoveItemEvent(top, ordinary, mock(Inventory.class), true);
+        listener.onInventoryMove(hopper);
+        assertFalse(hopper.isCancelled());
+        assertTrue(scheduled.isEmpty());
+    }
+
+    @Test
+    void safeInternalCursorMovementDoesNotTriggerRejectionOrRefresh() {
+        var pickup = click(30, ClickType.LEFT, InventoryAction.PICKUP_ALL, -1);
+        listener.onInventoryClick(pickup);
+        assertFalse(pickup.isCancelled());
+        contents[3] = null;
+        cursor.set(egg);
+        var place = click(31, ClickType.LEFT, InventoryAction.PLACE_ALL, -1);
+        listener.onInventoryClick(place);
+        assertFalse(place.isCancelled());
+        var drag = new org.bukkit.event.inventory.InventoryDragEvent(view, null, egg, false, Map.of(31, egg));
+        listener.onInventoryDrag(drag);
+        assertFalse(drag.isCancelled());
+        assertTrue(scheduled.isEmpty());
+        new CapturedMobInventoryService(items, PluginSettings.from(Map.of()))
+            .reconcile(player, manager.player(owner, "Tamer"));
+        assertSame(egg, cursor.get());
+        verify(inventory, never()).addItem(any(ItemStack[].class));
+    }
+
+    @Test
+    void cursorTransferAndExistingCancellationPreserveCustodyAndResynchronize() throws Exception {
+        var before = manager.snapshot();
+        byte[] bytes = Files.readAllBytes(stateFile);
+        contents[3] = null;
+        cursor.set(egg);
+        var external = click(0, ClickType.LEFT, InventoryAction.PLACE_ALL, -1);
+        listener.onInventoryClick(external);
+        assertTrue(external.isCancelled());
+        var cancelled = click(31, ClickType.LEFT, InventoryAction.PLACE_ALL, -1);
+        cancelled.setCancelled(true);
+        listener.onInventoryClick(cancelled);
+        assertTrue(cancelled.isCancelled());
+        assertEquals(1, scheduled.size());
+        scheduled.remove(0).run();
+        assertSame(egg, cursor.get());
+        assertEquals(before, manager.snapshot());
+        assertArrayEquals(bytes, Files.readAllBytes(stateFile));
+        verify(player).updateInventory();
+        verify(top, never()).setItem(anyInt(), nullable(ItemStack.class));
+    }
+
+    private InventoryClickEvent click(int raw, ClickType click, InventoryAction action, int button) {
+        return new InventoryClickEvent(view, InventoryType.SlotType.CONTAINER, raw, click, action, button);
+    }
+
+    private ItemStack egg(UUID id, UUID captured) {
+        ItemStack item = mock(ItemStack.class);
+        markEgg(item, id, captured);
+        return item;
+    }
+
+    private void markEgg(ItemStack item, UUID id, UUID captured) {
+        ItemMeta meta = mock(ItemMeta.class);
+        PersistentDataContainer data = mock(PersistentDataContainer.class);
+        when(item.clone()).thenReturn(item);
+        when(item.hasItemMeta()).thenReturn(true);
+        when(item.getItemMeta()).thenReturn(meta);
+        var amount = new java.util.concurrent.atomic.AtomicInteger(1);
+        when(item.getAmount()).thenAnswer(call -> amount.get());
+        doAnswer(call -> { amount.set(call.getArgument(0)); return null; }).when(item).setAmount(anyInt());
+        when(meta.getPersistentDataContainer()).thenReturn(data);
+        when(data.get(new NamespacedKey("spigottyrant", "captured-owner"), PersistentDataType.STRING))
+            .thenReturn(id.toString());
+        when(data.get(new NamespacedKey("spigottyrant", "captured-id"), PersistentDataType.STRING))
+            .thenReturn(captured.toString());
+    }
+}

src/test/java/games/dmg/spigottyrant/TamerListenerTest.java

@@ -49,7 +49,7 @@ final class TamerListenerTest {
         CapturedMobItemService capturedItems = mock(CapturedMobItemService.class);
         TamerListener listener = new TamerListener(
             manager, abilityItems, capturedItems, new CapturedMobService(),
-            PluginSettings.from(Map.of()), mock(Server.class)
+            PluginSettings.from(Map.of()), mock(Server.class), Runnable::run
         );
 
         listener.onCapture(event);