diff --git a/src/battle-scene.ts b/src/battle-scene.ts
index 68b796ee5c0..97363838c9c 100644
--- a/src/battle-scene.ts
+++ b/src/battle-scene.ts
@@ -1240,7 +1240,7 @@ export default class BattleScene extends SceneBase {
         this.field.add(newTrainer);
       }
     } else {
-      if (!this.gameMode.hasTrainers) {
+      if (!this.gameMode.hasTrainers || (Overrides.DISABLE_TRAINERS_OVERRIDE && isNullOrUndefined(trainerData))) {
         newBattleType = BattleType.WILD;
       } else if (battleType === undefined) {
         newBattleType = this.gameMode.isWaveTrainer(newWaveIndex, this.arena) ? BattleType.TRAINER : BattleType.WILD;
diff --git a/src/overrides.ts b/src/overrides.ts
index e53d3b766c4..aacd36b922e 100644
--- a/src/overrides.ts
+++ b/src/overrides.ts
@@ -244,6 +244,11 @@ class DefaultOverrides {
    * Note that, for all items in the array, `count` is not used.
    */
   readonly ITEM_REWARD_OVERRIDE: ModifierOverride[] = [];
+
+  /**
+   * If `true`, disable all non-scripted opponent trainer encounters.
+   */
+  readonly DISABLE_TRAINERS_OVERRIDE: boolean = false;
 }
 
 export const defaultOverrides = new DefaultOverrides();
diff --git a/test/utils/gameManager.ts b/test/utils/gameManager.ts
index 1a229969800..05fb82f6516 100644
--- a/test/utils/gameManager.ts
+++ b/test/utils/gameManager.ts
@@ -120,9 +120,11 @@ export default class GameManager {
     this.settings = new SettingsHelper(this);
     this.reload = new ReloadHelper(this);
     this.modifiers = new ModifierHelper(this);
+    this.field = new FieldHelper(this);
+    this.override.sanitizeOverrides();
 
-    // Sanitize overrides for each test
-    this.override.mysteryEncounterChance(0).moveset([]).enemyMoveset([]).startingHeldItems([]).enemyHeldItems([]);
+    // Disables Mystery Encounters on all tests (can be overridden at test level)
+    this.override.mysteryEncounterChance(0);
 
     global.fetch = vi.fn(MockFetch) as any;
   }
diff --git a/test/utils/helpers/overridesHelper.ts b/test/utils/helpers/overridesHelper.ts
index 47358738048..2f318ff8035 100644
--- a/test/utils/helpers/overridesHelper.ts
+++ b/test/utils/helpers/overridesHelper.ts
@@ -1,12 +1,9 @@
 import type { Variant } from "#app/data/variant";
 import { Weather } from "#app/data/weather";
-import { Abilities } from "#app/enums/abilities";
-import * as GameMode from "#app/game-mode";
-import type { GameModes } from "#app/game-mode";
-import { getGameMode } from "#app/game-mode";
+import { Abilities } from "#enums/abilities";
 import type { ModifierOverride } from "#app/modifier/modifier-type";
 import type { BattleStyle } from "#app/overrides";
-import Overrides from "#app/overrides";
+import Overrides, { defaultOverrides } from "#app/overrides";
 import type { Unlockables } from "#app/system/unlockables";
 import { Biome } from "#enums/biome";
 import { Moves } from "#enums/moves";
@@ -15,8 +12,9 @@ import type { MysteryEncounterType } from "#enums/mystery-encounter-type";
 import { Species } from "#enums/species";
 import { StatusEffect } from "#enums/status-effect";
 import type { WeatherType } from "#enums/weather-type";
-import { vi } from "vitest";
-import { GameManagerHelper } from "./gameManagerHelper";
+import { expect, vi } from "vitest";
+import { GameManagerHelper } from "#test/utils/helpers/gameManagerHelper";
+import { shiftCharCodes } from "#app/utils";
 
 /**
  * Helper to handle overrides in tests
@@ -226,12 +224,7 @@ export class OverridesHelper extends GameManagerHelper {
    * @returns `this`
    */
   public disableTrainerWaves(): this {
-    const realFn = getGameMode;
-    vi.spyOn(GameMode, "getGameMode").mockImplementation((gameMode: GameModes) => {
-      const mode = realFn(gameMode);
-      mode.hasTrainers = false;
-      return mode;
-    });
+    vi.spyOn(Overrides, "DISABLE_TRAINERS_OVERRIDE", "get").mockReturnValue(true);
     this.log("Standard trainer waves are disabled!");
     return this;
   }
@@ -263,11 +256,8 @@ export class OverridesHelper extends GameManagerHelper {
    * @returns `this`
    */
   public seed(seed: string): this {
-    vi.spyOn(this.game.scene, "resetSeed").mockImplementation(() => {
-      this.game.scene.waveSeed = seed;
-      Phaser.Math.RND.sow([ seed ]);
-      this.game.scene.rngCounter = 0;
-    });
+    // Shift the seed here with a negative wave number, to compensate for `resetSeed()` shifting the seed itself.
+    this.game.scene.setSeed(shiftCharCodes(seed, (this.game.scene.currentBattle?.waveIndex ?? 0) * -1));
     this.game.scene.resetSeed();
     this.log(`Seed set to "${seed}"!`);
     return this;
@@ -539,4 +529,14 @@ export class OverridesHelper extends GameManagerHelper {
   private log(...params: any[]) {
     console.log("Overrides:", ...params);
   }
+
+  public sanitizeOverrides(): void {
+    for (const key of Object.keys(defaultOverrides)) {
+      if (Overrides[key] !== defaultOverrides[key]) {
+        vi.spyOn(Overrides, key as any, "get").mockReturnValue(defaultOverrides[key]);
+      }
+    }
+    expect(Overrides).toEqual(defaultOverrides);
+    this.log("Sanitizing all overrides!");
+  }
 }
diff --git a/test/vitest.setup.ts b/test/vitest.setup.ts
index 9350f7f0eaf..f886a03d9bb 100644
--- a/test/vitest.setup.ts
+++ b/test/vitest.setup.ts
@@ -10,9 +10,10 @@ vi.mock("#app/overrides", async (importOriginal) => {
 
   return {
     default: defaultOverrides,
-    defaultOverrides,
-  // eslint-disable-next-line @typescript-eslint/consistent-type-imports
-  } satisfies typeof import("#app/overrides");
+    // Export `defaultOverrides` as a *copy*.
+    // This ensures we can easily reset `overrides` back to its default values after modifying it.
+    defaultOverrides: { ...defaultOverrides },
+  } satisfies typeof import("#app/overrides"); // eslint-disable-line
 });
 
 /**