diff --git a/test/abilities/ability_activation_order.test.ts b/test/abilities/ability_activation_order.test.ts
index 8344ba6be11..0f92bd974a9 100644
--- a/test/abilities/ability_activation_order.test.ts
+++ b/test/abilities/ability_activation_order.test.ts
@@ -1,7 +1,7 @@
 import { AbilityId } from "#enums/ability-id";
+import { HeldItemId } from "#enums/held-item-id";
 import { MoveId } from "#enums/move-id";
 import { SpeciesId } from "#enums/species-id";
-import { Stat } from "#enums/stat";
 import { WeatherType } from "#enums/weather-type";
 import { GameManager } from "#test/testUtils/gameManager";
 import Phaser from "phaser";
@@ -48,7 +48,7 @@ describe("Ability Activation Order", () => {
       .enemySpecies(SpeciesId.MAGIKARP)
       .enemyAbility(AbilityId.DROUGHT)
       .ability(AbilityId.DRIZZLE)
-      .startingHeldItems([{ name: "BASE_STAT_BOOSTER", type: Stat.SPD, count: 100 }]);
+      .startingHeldItems([{ entry: HeldItemId.CARBOS, count: 100 }]);
 
     await game.classicMode.startBattle([SpeciesId.MAGIKARP]);
     expect(game.scene.arena.weather?.weatherType).toBe(WeatherType.SUNNY);
@@ -61,7 +61,7 @@ describe("Ability Activation Order", () => {
       .enemySpecies(SpeciesId.DITTO)
       .enemyAbility(AbilityId.DROUGHT)
       .ability(AbilityId.DRIZZLE)
-      .startingHeldItems([{ name: "SPECIES_STAT_BOOSTER", type: "QUICK_POWDER" }]);
+      .startingHeldItems([{ entry: HeldItemId.QUICK_POWDER }]);
 
     await game.classicMode.startBattle([SpeciesId.DITTO]);
     expect(game.scene.arena.weather?.weatherType).toBe(WeatherType.SUNNY);
diff --git a/test/abilities/arena_trap.test.ts b/test/abilities/arena_trap.test.ts
index c47cf3cd327..e0e1fc60a97 100644
--- a/test/abilities/arena_trap.test.ts
+++ b/test/abilities/arena_trap.test.ts
@@ -2,6 +2,7 @@ import { allAbilities } from "#data/data-lists";
 import { AbilityId } from "#enums/ability-id";
 import { MoveId } from "#enums/move-id";
 import { SpeciesId } from "#enums/species-id";
+import { TrainerItemId } from "#enums/trainer-item-id";
 import { GameManager } from "#test/testUtils/gameManager";
 import Phaser from "phaser";
 import { afterEach, beforeAll, beforeEach, describe, expect, it, vi } from "vitest";
@@ -46,7 +47,7 @@ describe("Abilities - Arena Trap", () => {
   });
 
   it("should guarantee double battle with any one LURE", async () => {
-    game.override.startingModifier([{ name: "LURE" }]).startingWave(2);
+    game.override.startingTrainerItems([{ entry: TrainerItemId.LURE }]).startingWave(2);
 
     await game.classicMode.startBattle();
 
diff --git a/test/abilities/competitive.test.ts b/test/abilities/competitive.test.ts
index 7dcc677a74e..78508e486cd 100644
--- a/test/abilities/competitive.test.ts
+++ b/test/abilities/competitive.test.ts
@@ -1,4 +1,5 @@
 import { AbilityId } from "#enums/ability-id";
+import { HeldItemId } from "#enums/held-item-id";
 import { MoveId } from "#enums/move-id";
 import { SpeciesId } from "#enums/species-id";
 import { Stat } from "#enums/stat";
@@ -59,7 +60,7 @@ describe("Abilities - Competitive", () => {
   });
 
   it("white herb should remove only the negative effects", async () => {
-    game.override.startingHeldItems([{ name: "WHITE_HERB" }]);
+    game.override.startingHeldItems([{ entry: HeldItemId.WHITE_HERB }]);
     await game.classicMode.startBattle([SpeciesId.FLYGON]);
 
     const playerPokemon = game.scene.getPlayerPokemon()!;
diff --git a/test/abilities/defiant.test.ts b/test/abilities/defiant.test.ts
index 44187429e2b..2e202d43fe5 100644
--- a/test/abilities/defiant.test.ts
+++ b/test/abilities/defiant.test.ts
@@ -1,4 +1,5 @@
 import { AbilityId } from "#enums/ability-id";
+import { HeldItemId } from "#enums/held-item-id";
 import { MoveId } from "#enums/move-id";
 import { SpeciesId } from "#enums/species-id";
 import { Stat } from "#enums/stat";
@@ -58,7 +59,7 @@ describe("Abilities - Defiant", () => {
   });
 
   it("white herb should remove only the negative effects", async () => {
-    game.override.startingHeldItems([{ name: "WHITE_HERB" }]);
+    game.override.startingHeldItems([{ entry: HeldItemId.WHITE_HERB }]);
     await game.classicMode.startBattle([SpeciesId.FLYGON]);
 
     const playerPokemon = game.scene.getPlayerPokemon()!;
diff --git a/test/abilities/flower_veil.test.ts b/test/abilities/flower_veil.test.ts
index e890ea24fad..b8844ce1025 100644
--- a/test/abilities/flower_veil.test.ts
+++ b/test/abilities/flower_veil.test.ts
@@ -2,6 +2,7 @@ import { allAbilities, allMoves } from "#data/data-lists";
 import { AbilityId } from "#enums/ability-id";
 import { BattlerIndex } from "#enums/battler-index";
 import { BattlerTagType } from "#enums/battler-tag-type";
+import { HeldItemId } from "#enums/held-item-id";
 import { MoveId } from "#enums/move-id";
 import { SpeciesId } from "#enums/species-id";
 import { Stat } from "#enums/stat";
@@ -44,7 +45,7 @@ describe("Abilities - Flower Veil", () => {
     game.override
       .enemyMoveset([MoveId.TACKLE, MoveId.SPLASH])
       .moveset([MoveId.REST, MoveId.SPLASH])
-      .startingHeldItems([{ name: "FLAME_ORB" }]);
+      .startingHeldItems([{ entry: HeldItemId.FLAME_ORB }]);
     await game.classicMode.startBattle([SpeciesId.BULBASAUR]);
     const user = game.scene.getPlayerPokemon()!;
     game.move.select(MoveId.REST);
diff --git a/test/abilities/illuminate.test.ts b/test/abilities/illuminate.test.ts
index 0fb31379542..6e84df7bfd8 100644
--- a/test/abilities/illuminate.test.ts
+++ b/test/abilities/illuminate.test.ts
@@ -1,6 +1,7 @@
 import { AbilityId } from "#enums/ability-id";
 import { MoveId } from "#enums/move-id";
 import { Stat } from "#enums/stat";
+import { TrainerItemId } from "#enums/trainer-item-id";
 import { GameManager } from "#test/testUtils/gameManager";
 import Phaser from "phaser";
 import { afterEach, beforeAll, beforeEach, describe, expect, it } from "vitest";
@@ -45,7 +46,7 @@ describe("Abilities - Illuminate", () => {
   });
 
   it("should guarantee double battle with any one LURE", async () => {
-    game.override.startingModifier([{ name: "LURE" }]).startingWave(2);
+    game.override.startingTrainerItems([{ entry: TrainerItemId.LURE }]).startingWave(2);
 
     await game.classicMode.startBattle();
 
diff --git a/test/abilities/illusion.test.ts b/test/abilities/illusion.test.ts
index 0624c5e19f4..01aae92ed6f 100644
--- a/test/abilities/illusion.test.ts
+++ b/test/abilities/illusion.test.ts
@@ -1,5 +1,6 @@
 import { Gender } from "#data/gender";
 import { AbilityId } from "#enums/ability-id";
+import { HeldItemId } from "#enums/held-item-id";
 import { MoveId } from "#enums/move-id";
 import { PokeballType } from "#enums/pokeball";
 import { SpeciesId } from "#enums/species-id";
@@ -28,9 +29,9 @@ describe("Abilities - Illusion", () => {
       .enemySpecies(SpeciesId.ZORUA)
       .enemyAbility(AbilityId.ILLUSION)
       .enemyMoveset(MoveId.TACKLE)
-      .enemyHeldItems([{ name: "WIDE_LENS", count: 3 }])
+      .enemyHeldItems([{ entry: HeldItemId.WIDE_LENS, count: 3 }])
       .moveset([MoveId.WORRY_SEED, MoveId.SOAK, MoveId.TACKLE])
-      .startingHeldItems([{ name: "WIDE_LENS", count: 3 }]);
+      .startingHeldItems([{ entry: HeldItemId.WIDE_LENS, count: 3 }]);
   });
 
   it("creates illusion at the start", async () => {
diff --git a/test/abilities/no_guard.test.ts b/test/abilities/no_guard.test.ts
index f6f55ce3b80..614f043508f 100644
--- a/test/abilities/no_guard.test.ts
+++ b/test/abilities/no_guard.test.ts
@@ -3,6 +3,7 @@ import { BattlerIndex } from "#enums/battler-index";
 import { HitCheckResult } from "#enums/hit-check-result";
 import { MoveId } from "#enums/move-id";
 import { SpeciesId } from "#enums/species-id";
+import { TrainerItemId } from "#enums/trainer-item-id";
 import { MoveEffectPhase } from "#phases/move-effect-phase";
 import { MoveEndPhase } from "#phases/move-end-phase";
 import { GameManager } from "#test/testUtils/gameManager";
@@ -54,7 +55,7 @@ describe("Abilities - No Guard", () => {
   });
 
   it("should guarantee double battle with any one LURE", async () => {
-    game.override.startingModifier([{ name: "LURE" }]).startingWave(2);
+    game.override.startingTrainerItems([{ entry: TrainerItemId.LURE }]).startingWave(2);
 
     await game.classicMode.startBattle();
 
diff --git a/test/abilities/normal-move-type-change.test.ts b/test/abilities/normal-move-type-change.test.ts
index aa673ddde29..2d393218a9b 100644
--- a/test/abilities/normal-move-type-change.test.ts
+++ b/test/abilities/normal-move-type-change.test.ts
@@ -2,9 +2,11 @@ import { TYPE_BOOST_ITEM_BOOST_PERCENT } from "#app/constants";
 import { allAbilities, allMoves } from "#data/data-lists";
 import { AbilityId } from "#enums/ability-id";
 import { BattlerIndex } from "#enums/battler-index";
+import { HeldItemId } from "#enums/held-item-id";
 import { MoveId } from "#enums/move-id";
 import { PokemonType } from "#enums/pokemon-type";
 import { SpeciesId } from "#enums/species-id";
+import { attackTypeToHeldItem } from "#items/attack-type-booster";
 import { GameManager } from "#test/testUtils/gameManager";
 import { toDmgValue } from "#utils/common";
 import Phaser from "phaser";
@@ -151,7 +153,7 @@ describe.each([
   });
 
   it("should not be affected by silk scarf after changing the move's type", async () => {
-    game.override.startingHeldItems([{ name: "ATTACK_TYPE_BOOSTER", count: 1, type: PokemonType.NORMAL }]);
+    game.override.startingHeldItems([{ entry: HeldItemId.SILK_SCARF }]);
     await game.classicMode.startBattle();
 
     const testMoveInstance = allMoves[MoveId.TACKLE];
@@ -170,7 +172,7 @@ describe.each([
   });
 
   it("should be affected by the type boosting item after changing the move's type", async () => {
-    game.override.startingHeldItems([{ name: "ATTACK_TYPE_BOOSTER", count: 1, type: ty }]);
+    game.override.startingHeldItems([{ entry: attackTypeToHeldItem[ty] }]);
     await game.classicMode.startBattle();
 
     // get the power boost from the ability so we can compare it to the item
diff --git a/test/abilities/normalize.test.ts b/test/abilities/normalize.test.ts
index 1128dd1a562..6c19f8168e5 100644
--- a/test/abilities/normalize.test.ts
+++ b/test/abilities/normalize.test.ts
@@ -1,6 +1,7 @@
 import { TYPE_BOOST_ITEM_BOOST_PERCENT } from "#app/constants";
 import { allMoves } from "#data/data-lists";
 import { AbilityId } from "#enums/ability-id";
+import { HeldItemId } from "#enums/held-item-id";
 import { MoveId } from "#enums/move-id";
 import { PokemonType } from "#enums/pokemon-type";
 import { SpeciesId } from "#enums/species-id";
@@ -45,9 +46,7 @@ describe("Abilities - Normalize", () => {
   });
 
   it("should not apply the old type boost item after changing a move's type", async () => {
-    game.override
-      .startingHeldItems([{ name: "ATTACK_TYPE_BOOSTER", count: 1, type: PokemonType.GRASS }])
-      .moveset([MoveId.LEAFAGE]);
+    game.override.startingHeldItems([{ entry: HeldItemId.MIRACLE_SEED }]).moveset([MoveId.LEAFAGE]);
 
     const powerSpy = vi.spyOn(allMoves[MoveId.LEAFAGE], "calculateBattlePower");
     await game.classicMode.startBattle([SpeciesId.MAGIKARP]);
@@ -59,9 +58,7 @@ describe("Abilities - Normalize", () => {
   });
 
   it("should apply silk scarf's power boost after changing a move's type", async () => {
-    game.override
-      .startingHeldItems([{ name: "ATTACK_TYPE_BOOSTER", count: 1, type: PokemonType.NORMAL }])
-      .moveset([MoveId.LEAFAGE]);
+    game.override.startingHeldItems([{ entry: HeldItemId.SILK_SCARF }]).moveset([MoveId.LEAFAGE]);
 
     const powerSpy = vi.spyOn(allMoves[MoveId.LEAFAGE], "calculateBattlePower");
     await game.classicMode.startBattle([SpeciesId.MAGIKARP]);
diff --git a/test/abilities/protosynthesis.test.ts b/test/abilities/protosynthesis.test.ts
index 5629ea503d7..e02e8fdcf2b 100644
--- a/test/abilities/protosynthesis.test.ts
+++ b/test/abilities/protosynthesis.test.ts
@@ -4,6 +4,7 @@ import { MoveId } from "#enums/move-id";
 import { Nature } from "#enums/nature";
 import { SpeciesId } from "#enums/species-id";
 import { Stat } from "#enums/stat";
+import { TrainerItemId } from "#enums/trainer-item-id";
 import { GameManager } from "#test/testUtils/gameManager";
 import Phaser from "phaser";
 import { afterEach, beforeAll, beforeEach, describe, expect, it } from "vitest";
@@ -37,7 +38,7 @@ describe("Abilities - Protosynthesis", () => {
   it("should not consider temporary items when determining which stat to boost", async () => {
     // Mew has uniform base stats
     game.override
-      .startingModifier([{ name: "TEMP_STAT_STAGE_BOOSTER", type: Stat.DEF }])
+      .startingTrainerItems([{ entry: TrainerItemId.X_DEFENSE }])
       .enemyMoveset(MoveId.SUNNY_DAY)
       .startingLevel(100)
       .enemyLevel(100);
diff --git a/test/abilities/unburden.test.ts b/test/abilities/unburden.test.ts
index 647cd28855d..2ce6841ca3e 100644
--- a/test/abilities/unburden.test.ts
+++ b/test/abilities/unburden.test.ts
@@ -76,7 +76,7 @@ describe("Abilities - Unburden", () => {
   it("should activate when a berry is eaten, even if Berry Pouch preserves the berry", async () => {
     game.override
       .enemyMoveset(MoveId.FALSE_SWIPE)
-      .startingHeldItems([{ entry: TrainerItemId.BERRY_POUCH, count: 5850 }]);
+      .startingTrainerItems([{ entry: TrainerItemId.BERRY_POUCH, count: 5850 }]);
     await game.classicMode.startBattle([SpeciesId.TREECKO]);
 
     const playerPokemon = game.scene.getPlayerPokemon()!;
diff --git a/test/abilities/wimp_out.test.ts b/test/abilities/wimp_out.test.ts
index fc27bf10c86..57f9d786654 100644
--- a/test/abilities/wimp_out.test.ts
+++ b/test/abilities/wimp_out.test.ts
@@ -4,6 +4,7 @@ import { ArenaTagSide } from "#enums/arena-tag-side";
 import { ArenaTagType } from "#enums/arena-tag-type";
 import { BattlerIndex } from "#enums/battler-index";
 import { BattlerTagType } from "#enums/battler-tag-type";
+import { HeldItemId } from "#enums/held-item-id";
 import { MoveId } from "#enums/move-id";
 import { SpeciesId } from "#enums/species-id";
 import { Stat } from "#enums/stat";
@@ -205,7 +206,7 @@ describe("Abilities - Wimp Out", () => {
       game.override
         .moveset([MoveId.DOUBLE_EDGE])
         .enemyMoveset([MoveId.SPLASH])
-        .startingHeldItems([{ name: "SHELL_BELL", count: 4 }]);
+        .startingHeldItems([{ entry: HeldItemId.SHELL_BELL, count: 4 }]);
       await game.classicMode.startBattle([SpeciesId.WIMPOD, SpeciesId.TYRUNT]);
 
       const wimpod = game.scene.getPlayerPokemon()!;
@@ -430,7 +431,7 @@ describe("Abilities - Wimp Out", () => {
   });
 
   it("triggers after last hit of multi hit move (multi lens)", async () => {
-    game.override.enemyMoveset(MoveId.TACKLE).enemyHeldItems([{ name: "MULTI_LENS", count: 1 }]);
+    game.override.enemyMoveset(MoveId.TACKLE).enemyHeldItems([{ entry: HeldItemId.MULTI_LENS, count: 1 }]);
     await game.classicMode.startBattle([SpeciesId.WIMPOD, SpeciesId.TYRUNT]);
 
     game.scene.getPlayerPokemon()!.hp *= 0.51;
diff --git a/test/items/metal_powder.test.ts b/test/items/metal_powder.test.ts
index 17baa057fd5..3aa35d1b983 100644
--- a/test/items/metal_powder.test.ts
+++ b/test/items/metal_powder.test.ts
@@ -1,7 +1,9 @@
 import { modifierTypes } from "#data/data-lists";
+import { HeldItemId } from "#enums/held-item-id";
 import { SpeciesId } from "#enums/species-id";
 import { Stat } from "#enums/stat";
-import { SpeciesStatBoosterModifier } from "#modifiers/modifier";
+import { applyHeldItems } from "#items/all-held-items";
+import { HeldItemEffect } from "#items/held-item";
 import i18next from "#plugins/i18n";
 import { GameManager } from "#test/testUtils/gameManager";
 import { NumberHolder } from "#utils/common";
@@ -29,7 +31,7 @@ describe("Items - Metal Powder", () => {
   });
 
   it("METAL_POWDER activates in battle correctly", async () => {
-    game.override.startingHeldItems([{ name: "RARE_SPECIES_STAT_BOOSTER", type: "METAL_POWDER" }]);
+    game.override.startingHeldItems([{ entry: HeldItemId.METAL_POWDER }]);
     const consoleSpy = vi.spyOn(console, "log");
     await game.classicMode.startBattle([SpeciesId.DITTO]);
 
@@ -90,7 +92,7 @@ describe("Items - Metal Powder", () => {
 
     // Making sure modifier is not applied without holding item
     const defValue = new NumberHolder(defStat);
-    game.scene.applyModifiers(SpeciesStatBoosterModifier, true, partyMember, Stat.DEF, defValue);
+    applyHeldItems(HeldItemEffect.STAT_BOOST, { pokemon: partyMember, stat: Stat.DEF, statValue: defValue });
 
     expect(defValue.value / defStat).toBe(1);
 
@@ -99,7 +101,7 @@ describe("Items - Metal Powder", () => {
       modifierTypes.RARE_SPECIES_STAT_BOOSTER().generateType([], ["METAL_POWDER"])!.newModifier(partyMember),
       true,
     );
-    game.scene.applyModifiers(SpeciesStatBoosterModifier, true, partyMember, Stat.DEF, defValue);
+    applyHeldItems(HeldItemEffect.STAT_BOOST, { pokemon: partyMember, stat: Stat.DEF, statValue: defValue });
 
     expect(defValue.value / defStat).toBe(2);
   });
@@ -123,7 +125,7 @@ describe("Items - Metal Powder", () => {
 
     // Making sure modifier is not applied without holding item
     const defValue = new NumberHolder(defStat);
-    game.scene.applyModifiers(SpeciesStatBoosterModifier, true, partyMember, Stat.DEF, defValue);
+    applyHeldItems(HeldItemEffect.STAT_BOOST, { pokemon: partyMember, stat: Stat.DEF, statValue: defValue });
 
     expect(defValue.value / defStat).toBe(1);
 
@@ -132,7 +134,7 @@ describe("Items - Metal Powder", () => {
       modifierTypes.RARE_SPECIES_STAT_BOOSTER().generateType([], ["METAL_POWDER"])!.newModifier(partyMember),
       true,
     );
-    game.scene.applyModifiers(SpeciesStatBoosterModifier, true, partyMember, Stat.DEF, defValue);
+    applyHeldItems(HeldItemEffect.STAT_BOOST, { pokemon: partyMember, stat: Stat.DEF, statValue: defValue });
 
     expect(defValue.value / defStat).toBe(2);
   });
@@ -156,7 +158,7 @@ describe("Items - Metal Powder", () => {
 
     // Making sure modifier is not applied without holding item
     const defValue = new NumberHolder(defStat);
-    game.scene.applyModifiers(SpeciesStatBoosterModifier, true, partyMember, Stat.DEF, defValue);
+    applyHeldItems(HeldItemEffect.STAT_BOOST, { pokemon: partyMember, stat: Stat.DEF, statValue: defValue });
 
     expect(defValue.value / defStat).toBe(1);
 
@@ -165,7 +167,7 @@ describe("Items - Metal Powder", () => {
       modifierTypes.RARE_SPECIES_STAT_BOOSTER().generateType([], ["METAL_POWDER"])!.newModifier(partyMember),
       true,
     );
-    game.scene.applyModifiers(SpeciesStatBoosterModifier, true, partyMember, Stat.DEF, defValue);
+    applyHeldItems(HeldItemEffect.STAT_BOOST, { pokemon: partyMember, stat: Stat.DEF, statValue: defValue });
 
     expect(defValue.value / defStat).toBe(2);
   });
@@ -179,7 +181,7 @@ describe("Items - Metal Powder", () => {
 
     // Making sure modifier is not applied without holding item
     const defValue = new NumberHolder(defStat);
-    game.scene.applyModifiers(SpeciesStatBoosterModifier, true, partyMember, Stat.DEF, defValue);
+    applyHeldItems(HeldItemEffect.STAT_BOOST, { pokemon: partyMember, stat: Stat.DEF, statValue: defValue });
 
     expect(defValue.value / defStat).toBe(1);
 
@@ -188,7 +190,7 @@ describe("Items - Metal Powder", () => {
       modifierTypes.RARE_SPECIES_STAT_BOOSTER().generateType([], ["METAL_POWDER"])!.newModifier(partyMember),
       true,
     );
-    game.scene.applyModifiers(SpeciesStatBoosterModifier, true, partyMember, Stat.DEF, defValue);
+    applyHeldItems(HeldItemEffect.STAT_BOOST, { pokemon: partyMember, stat: Stat.DEF, statValue: defValue });
 
     expect(defValue.value / defStat).toBe(1);
   });
diff --git a/test/items/quick_powder.test.ts b/test/items/quick_powder.test.ts
index 6c8cb0751c3..4148a7df92c 100644
--- a/test/items/quick_powder.test.ts
+++ b/test/items/quick_powder.test.ts
@@ -1,7 +1,9 @@
 import { modifierTypes } from "#data/data-lists";
+import { HeldItemId } from "#enums/held-item-id";
 import { SpeciesId } from "#enums/species-id";
 import { Stat } from "#enums/stat";
-import { SpeciesStatBoosterModifier } from "#modifiers/modifier";
+import { applyHeldItems } from "#items/all-held-items";
+import { HeldItemEffect } from "#items/held-item";
 import i18next from "#plugins/i18n";
 import { GameManager } from "#test/testUtils/gameManager";
 import { NumberHolder } from "#utils/common";
@@ -29,7 +31,7 @@ describe("Items - Quick Powder", () => {
   });
 
   it("QUICK_POWDER activates in battle correctly", async () => {
-    game.override.startingHeldItems([{ name: "RARE_SPECIES_STAT_BOOSTER", type: "QUICK_POWDER" }]);
+    game.override.startingHeldItems([{ entry: HeldItemId.QUICK_POWDER }]);
     const consoleSpy = vi.spyOn(console, "log");
     await game.classicMode.startBattle([SpeciesId.DITTO]);
 
@@ -90,7 +92,7 @@ describe("Items - Quick Powder", () => {
 
     // Making sure modifier is not applied without holding item
     const spdValue = new NumberHolder(spdStat);
-    game.scene.applyModifiers(SpeciesStatBoosterModifier, true, partyMember, Stat.SPD, spdValue);
+    applyHeldItems(HeldItemEffect.STAT_BOOST, { pokemon: partyMember, stat: Stat.SPD, statValue: spdValue });
 
     expect(spdValue.value / spdStat).toBe(1);
 
@@ -99,7 +101,7 @@ describe("Items - Quick Powder", () => {
       modifierTypes.RARE_SPECIES_STAT_BOOSTER().generateType([], ["QUICK_POWDER"])!.newModifier(partyMember),
       true,
     );
-    game.scene.applyModifiers(SpeciesStatBoosterModifier, true, partyMember, Stat.SPD, spdValue);
+    applyHeldItems(HeldItemEffect.STAT_BOOST, { pokemon: partyMember, stat: Stat.SPD, statValue: spdValue });
 
     expect(spdValue.value / spdStat).toBe(2);
   });
@@ -123,7 +125,7 @@ describe("Items - Quick Powder", () => {
 
     // Making sure modifier is not applied without holding item
     const spdValue = new NumberHolder(spdStat);
-    game.scene.applyModifiers(SpeciesStatBoosterModifier, true, partyMember, Stat.SPD, spdValue);
+    applyHeldItems(HeldItemEffect.STAT_BOOST, { pokemon: partyMember, stat: Stat.SPD, statValue: spdValue });
 
     expect(spdValue.value / spdStat).toBe(1);
 
@@ -132,7 +134,7 @@ describe("Items - Quick Powder", () => {
       modifierTypes.RARE_SPECIES_STAT_BOOSTER().generateType([], ["QUICK_POWDER"])!.newModifier(partyMember),
       true,
     );
-    game.scene.applyModifiers(SpeciesStatBoosterModifier, true, partyMember, Stat.SPD, spdValue);
+    applyHeldItems(HeldItemEffect.STAT_BOOST, { pokemon: partyMember, stat: Stat.SPD, statValue: spdValue });
 
     expect(spdValue.value / spdStat).toBe(2);
   });
@@ -156,7 +158,7 @@ describe("Items - Quick Powder", () => {
 
     // Making sure modifier is not applied without holding item
     const spdValue = new NumberHolder(spdStat);
-    game.scene.applyModifiers(SpeciesStatBoosterModifier, true, partyMember, Stat.SPD, spdValue);
+    applyHeldItems(HeldItemEffect.STAT_BOOST, { pokemon: partyMember, stat: Stat.SPD, statValue: spdValue });
 
     expect(spdValue.value / spdStat).toBe(1);
 
@@ -165,7 +167,7 @@ describe("Items - Quick Powder", () => {
       modifierTypes.RARE_SPECIES_STAT_BOOSTER().generateType([], ["QUICK_POWDER"])!.newModifier(partyMember),
       true,
     );
-    game.scene.applyModifiers(SpeciesStatBoosterModifier, true, partyMember, Stat.SPD, spdValue);
+    applyHeldItems(HeldItemEffect.STAT_BOOST, { pokemon: partyMember, stat: Stat.SPD, statValue: spdValue });
 
     expect(spdValue.value / spdStat).toBe(2);
   });
@@ -179,7 +181,7 @@ describe("Items - Quick Powder", () => {
 
     // Making sure modifier is not applied without holding item
     const spdValue = new NumberHolder(spdStat);
-    game.scene.applyModifiers(SpeciesStatBoosterModifier, true, partyMember, Stat.SPD, spdValue);
+    applyHeldItems(HeldItemEffect.STAT_BOOST, { pokemon: partyMember, stat: Stat.SPD, statValue: spdValue });
 
     expect(spdValue.value / spdStat).toBe(1);
 
@@ -188,7 +190,7 @@ describe("Items - Quick Powder", () => {
       modifierTypes.RARE_SPECIES_STAT_BOOSTER().generateType([], ["QUICK_POWDER"])!.newModifier(partyMember),
       true,
     );
-    game.scene.applyModifiers(SpeciesStatBoosterModifier, true, partyMember, Stat.SPD, spdValue);
+    applyHeldItems(HeldItemEffect.STAT_BOOST, { pokemon: partyMember, stat: Stat.SPD, statValue: spdValue });
 
     expect(spdValue.value / spdStat).toBe(1);
   });
diff --git a/test/items/thick_club.test.ts b/test/items/thick_club.test.ts
index dd262600823..6fb1e6fbab7 100644
--- a/test/items/thick_club.test.ts
+++ b/test/items/thick_club.test.ts
@@ -2,6 +2,8 @@ import { modifierTypes } from "#data/data-lists";
 import { HeldItemId } from "#enums/held-item-id";
 import { SpeciesId } from "#enums/species-id";
 import { Stat } from "#enums/stat";
+import { applyHeldItems } from "#items/all-held-items";
+import { HeldItemEffect } from "#items/held-item";
 import i18next from "#plugins/i18n";
 import { GameManager } from "#test/testUtils/gameManager";
 import { NumberHolder, randInt } from "#utils/common";
@@ -90,7 +92,7 @@ describe("Items - Thick Club", () => {
 
     // Making sure modifier is not applied without holding item
     const atkValue = new NumberHolder(atkStat);
-    game.scene.applyModifiers(SpeciesStatBoosterModifier, true, partyMember, Stat.ATK, atkValue);
+    applyHeldItems(HeldItemEffect.STAT_BOOST, { pokemon: partyMember, stat: Stat.ATK, statValue: atkValue });
 
     expect(atkValue.value / atkStat).toBe(1);
 
@@ -99,7 +101,7 @@ describe("Items - Thick Club", () => {
       modifierTypes.RARE_SPECIES_STAT_BOOSTER().generateType([], ["THICK_CLUB"])!.newModifier(partyMember),
       true,
     );
-    game.scene.applyModifiers(SpeciesStatBoosterModifier, true, partyMember, Stat.ATK, atkValue);
+    applyHeldItems(HeldItemEffect.STAT_BOOST, { pokemon: partyMember, stat: Stat.ATK, statValue: atkValue });
 
     expect(atkValue.value / atkStat).toBe(2);
   });
@@ -113,7 +115,7 @@ describe("Items - Thick Club", () => {
 
     // Making sure modifier is not applied without holding item
     const atkValue = new NumberHolder(atkStat);
-    game.scene.applyModifiers(SpeciesStatBoosterModifier, true, partyMember, Stat.ATK, atkValue);
+    applyHeldItems(HeldItemEffect.STAT_BOOST, { pokemon: partyMember, stat: Stat.ATK, statValue: atkValue });
 
     expect(atkValue.value / atkStat).toBe(1);
 
@@ -122,7 +124,7 @@ describe("Items - Thick Club", () => {
       modifierTypes.RARE_SPECIES_STAT_BOOSTER().generateType([], ["THICK_CLUB"])!.newModifier(partyMember),
       true,
     );
-    game.scene.applyModifiers(SpeciesStatBoosterModifier, true, partyMember, Stat.ATK, atkValue);
+    applyHeldItems(HeldItemEffect.STAT_BOOST, { pokemon: partyMember, stat: Stat.ATK, statValue: atkValue });
 
     expect(atkValue.value / atkStat).toBe(2);
   });
@@ -136,7 +138,7 @@ describe("Items - Thick Club", () => {
 
     // Making sure modifier is not applied without holding item
     const atkValue = new NumberHolder(atkStat);
-    game.scene.applyModifiers(SpeciesStatBoosterModifier, true, partyMember, Stat.ATK, atkValue);
+    applyHeldItems(HeldItemEffect.STAT_BOOST, { pokemon: partyMember, stat: Stat.ATK, statValue: atkValue });
 
     expect(atkValue.value / atkStat).toBe(1);
 
@@ -145,7 +147,7 @@ describe("Items - Thick Club", () => {
       modifierTypes.RARE_SPECIES_STAT_BOOSTER().generateType([], ["THICK_CLUB"])!.newModifier(partyMember),
       true,
     );
-    game.scene.applyModifiers(SpeciesStatBoosterModifier, true, partyMember, Stat.ATK, atkValue);
+    applyHeldItems(HeldItemEffect.STAT_BOOST, { pokemon: partyMember, stat: Stat.ATK, statValue: atkValue });
 
     expect(atkValue.value / atkStat).toBe(2);
   });
@@ -173,7 +175,7 @@ describe("Items - Thick Club", () => {
 
     // Making sure modifier is not applied without holding item
     const atkValue = new NumberHolder(atkStat);
-    game.scene.applyModifiers(SpeciesStatBoosterModifier, true, partyMember, Stat.ATK, atkValue);
+    applyHeldItems(HeldItemEffect.STAT_BOOST, { pokemon: partyMember, stat: Stat.ATK, statValue: atkValue });
 
     expect(atkValue.value / atkStat).toBe(1);
 
@@ -182,7 +184,7 @@ describe("Items - Thick Club", () => {
       modifierTypes.RARE_SPECIES_STAT_BOOSTER().generateType([], ["THICK_CLUB"])!.newModifier(partyMember),
       true,
     );
-    game.scene.applyModifiers(SpeciesStatBoosterModifier, true, partyMember, Stat.ATK, atkValue);
+    applyHeldItems(HeldItemEffect.STAT_BOOST, { pokemon: partyMember, stat: Stat.ATK, statValue: atkValue });
 
     expect(atkValue.value / atkStat).toBe(2);
   });
@@ -210,7 +212,7 @@ describe("Items - Thick Club", () => {
 
     // Making sure modifier is not applied without holding item
     const atkValue = new NumberHolder(atkStat);
-    game.scene.applyModifiers(SpeciesStatBoosterModifier, true, partyMember, Stat.ATK, atkValue);
+    applyHeldItems(HeldItemEffect.STAT_BOOST, { pokemon: partyMember, stat: Stat.ATK, statValue: atkValue });
 
     expect(atkValue.value / atkStat).toBe(1);
 
@@ -219,7 +221,7 @@ describe("Items - Thick Club", () => {
       modifierTypes.RARE_SPECIES_STAT_BOOSTER().generateType([], ["THICK_CLUB"])!.newModifier(partyMember),
       true,
     );
-    game.scene.applyModifiers(SpeciesStatBoosterModifier, true, partyMember, Stat.ATK, atkValue);
+    applyHeldItems(HeldItemEffect.STAT_BOOST, { pokemon: partyMember, stat: Stat.ATK, statValue: atkValue });
 
     expect(atkValue.value / atkStat).toBe(2);
   });
@@ -233,7 +235,7 @@ describe("Items - Thick Club", () => {
 
     // Making sure modifier is not applied without holding item
     const atkValue = new NumberHolder(atkStat);
-    game.scene.applyModifiers(SpeciesStatBoosterModifier, true, partyMember, Stat.ATK, atkValue);
+    applyHeldItems(HeldItemEffect.STAT_BOOST, { pokemon: partyMember, stat: Stat.ATK, statValue: atkValue });
 
     expect(atkValue.value / atkStat).toBe(1);
 
@@ -242,7 +244,7 @@ describe("Items - Thick Club", () => {
       modifierTypes.RARE_SPECIES_STAT_BOOSTER().generateType([], ["THICK_CLUB"])!.newModifier(partyMember),
       true,
     );
-    game.scene.applyModifiers(SpeciesStatBoosterModifier, true, partyMember, Stat.ATK, atkValue);
+    applyHeldItems(HeldItemEffect.STAT_BOOST, { pokemon: partyMember, stat: Stat.ATK, statValue: atkValue });
 
     expect(atkValue.value / atkStat).toBe(1);
   });
diff --git a/test/moves/electro_shot.test.ts b/test/moves/electro_shot.test.ts
index cb696b162d5..16ae47890e4 100644
--- a/test/moves/electro_shot.test.ts
+++ b/test/moves/electro_shot.test.ts
@@ -1,5 +1,6 @@
 import { AbilityId } from "#enums/ability-id";
 import { BattlerTagType } from "#enums/battler-tag-type";
+import { HeldItemId } from "#enums/held-item-id";
 import { MoveId } from "#enums/move-id";
 import { MoveResult } from "#enums/move-result";
 import { SpeciesId } from "#enums/species-id";
@@ -87,7 +88,7 @@ describe("Moves - Electro Shot", () => {
   });
 
   it("should only increase Sp. Atk once with Multi-Lens", async () => {
-    game.override.weather(WeatherType.RAIN).startingHeldItems([{ name: "MULTI_LENS", count: 1 }]);
+    game.override.weather(WeatherType.RAIN).startingHeldItems([{ entry: HeldItemId.MULTI_LENS }]);
 
     await game.classicMode.startBattle([SpeciesId.MAGIKARP]);
 
diff --git a/test/moves/tera_blast.test.ts b/test/moves/tera_blast.test.ts
index d6c16c31544..618e9e66d0a 100644
--- a/test/moves/tera_blast.test.ts
+++ b/test/moves/tera_blast.test.ts
@@ -1,6 +1,7 @@
 import { allMoves } from "#data/data-lists";
 import { AbilityId } from "#enums/ability-id";
 import { BattlerIndex } from "#enums/battler-index";
+import { HeldItemId } from "#enums/held-item-id";
 import { MoveId } from "#enums/move-id";
 import { PokemonType } from "#enums/pokemon-type";
 import { SpeciesId } from "#enums/species-id";
@@ -141,9 +142,7 @@ describe("Moves - Tera Blast", () => {
   });
 
   it("does not change its move category from stat changes due to held items", async () => {
-    game.override
-      .startingHeldItems([{ name: "SPECIES_STAT_BOOSTER", type: "THICK_CLUB" }])
-      .starterSpecies(SpeciesId.CUBONE);
+    game.override.startingHeldItems([{ entry: HeldItemId.THICK_CLUB }]).starterSpecies(SpeciesId.CUBONE);
     await game.classicMode.startBattle();
 
     const playerPokemon = game.scene.getPlayerPokemon()!;
diff --git a/test/moves/transform-imposter.test.ts b/test/moves/transform-imposter.test.ts
index c12542e64e9..cf582d482ce 100644
--- a/test/moves/transform-imposter.test.ts
+++ b/test/moves/transform-imposter.test.ts
@@ -3,7 +3,7 @@ import { AbilityId } from "#enums/ability-id";
 import { BattleType } from "#enums/battle-type";
 import { BattlerIndex } from "#enums/battler-index";
 import { BattlerTagType } from "#enums/battler-tag-type";
-import { BerryType } from "#enums/berry-type";
+import { HeldItemId } from "#enums/held-item-id";
 import { MoveId } from "#enums/move-id";
 import { MoveResult } from "#enums/move-result";
 import { PokemonType } from "#enums/pokemon-type";
@@ -128,7 +128,7 @@ describe("Transforming Effects", () => {
     it.todo("should copy the target's rage fist hit count");
 
     it("should not copy friendship, held items, nickname, level or non-volatile status effects", async () => {
-      game.override.enemyHeldItems([{ name: "BERRY", count: 1, type: BerryType.SITRUS }]);
+      game.override.enemyHeldItems([{ entry: HeldItemId.SITRUS_BERRY }]);
       await game.classicMode.startBattle([SpeciesId.DITTO]);
 
       const ditto = game.field.getPlayerPokemon();