diff --git a/src/data/pokemon-species.ts b/src/data/pokemon-species.ts
index 2b488f330c4..675372fa0af 100644
--- a/src/data/pokemon-species.ts
+++ b/src/data/pokemon-species.ts
@@ -177,12 +177,40 @@ export abstract class PokemonSpeciesForm {
     return this.type1 === type || (this.type2 !== null && this.type2 === type);
   }
 
+  /**
+   * Method to get the total number of abilities a Pokemon species has.
+   * @returns Number of abilities
+   */
   getAbilityCount(): integer {
-    return this.ability2 ? this.abilityHidden ? 3 : 2 : this.abilityHidden ? 2 : 1;
+    let count = 1;
+    if (this.ability2 !== Abilities.NONE) {
+      count += 1;
+    }
+    if (this.abilityHidden !== Abilities.NONE) {
+      count += 1;
+    }
+    return count;
   }
 
+  /**
+   * Method to get the ability of a Pokemon species.
+   * @param abilityIndex Which ability to get (should only be 0-2)
+   * @returns The id of the Ability
+   */
   getAbility(abilityIndex: integer): Abilities {
-    return !abilityIndex ? this.ability1 : abilityIndex === 1 && this.ability2 ? this.ability2 : this.abilityHidden;
+    let ret: Abilities;
+    if (abilityIndex === 0) {
+      ret = this.ability1;
+    } else if (abilityIndex === 1) {
+      if (this.ability2 !== Abilities.NONE) {
+        ret = this.ability2;
+      } else {
+        ret = this.abilityHidden;
+      }
+    } else {
+      ret = this.abilityHidden;
+    }
+    return ret;
   }
 
   getLevelMoves(): LevelMoves {
diff --git a/src/field/pokemon.ts b/src/field/pokemon.ts
index 6f78adc2224..70b1e6929ae 100644
--- a/src/field/pokemon.ts
+++ b/src/field/pokemon.ts
@@ -128,9 +128,19 @@ export default abstract class Pokemon extends Phaser.GameObjects.Container {
     this.species = species;
     this.pokeball = dataSource?.pokeball || PokeballType.POKEBALL;
     this.level = level;
-    this.abilityIndex = abilityIndex !== undefined
-      ? abilityIndex
-      : (species.abilityHidden && hasHiddenAbility ? species.ability2 ? 2 : 1 : species.ability2 ? randAbilityIndex : 0);
+    // Determine the ability index
+    if (abilityIndex !== undefined) {
+      this.abilityIndex = abilityIndex; // Use the provided ability index if it is defined
+    } else {
+      // If abilityIndex is not provided, determine it based on species and hidden ability
+      if (species.abilityHidden && hasHiddenAbility) {
+        // If the species has a hidden ability and the hidden ability is present
+        this.abilityIndex = species.ability2 ? 2 : 1; // Use ability index 2 if species has a second ability, otherwise use 1
+      } else {
+        // If there is no hidden ability or species does not have a hidden ability
+        this.abilityIndex = species.ability2 ? randAbilityIndex : 0; // Use random ability index if species has a second ability, otherwise use 0
+      }
+    }
     if (formIndex !== undefined) {
       this.formIndex = formIndex;
     }
diff --git a/src/test/internals.test.ts b/src/test/internals.test.ts
new file mode 100644
index 00000000000..a54b8b01544
--- /dev/null
+++ b/src/test/internals.test.ts
@@ -0,0 +1,43 @@
+import { afterEach, beforeAll, beforeEach, describe, expect, it } from "vitest";
+import Phaser from "phaser";
+import GameManager from "#app/test/utils/gameManager";
+import { Species } from "#app/enums/species.js";
+import { Abilities } from "#app/enums/abilities.js";
+
+describe("Internals", () => {
+  let phaserGame: Phaser.Game;
+  let game: GameManager;
+
+  beforeAll(() => {
+    phaserGame = new Phaser.Game({
+      type: Phaser.HEADLESS,
+    });
+  });
+
+  afterEach(() => {
+    game.phaseInterceptor.restoreOg();
+  });
+
+  beforeEach(() => {
+    game = new GameManager(phaserGame);
+  });
+
+  it("should provide Eevee with 3 defined abilities", async () => {
+    await game.runToSummon([Species.EEVEE]);
+    const eevee = game.scene.getPlayerPokemon();
+
+    expect(eevee.getSpeciesForm().getAbilityCount()).toBe(3);
+
+    expect(eevee.getSpeciesForm().getAbility(0)).toBe(Abilities.RUN_AWAY);
+    expect(eevee.getSpeciesForm().getAbility(1)).toBe(Abilities.ADAPTABILITY);
+    expect(eevee.getSpeciesForm().getAbility(2)).toBe(Abilities.ANTICIPATION);
+  });
+
+  it("should set Eeeve abilityIndex between 0-2", async () => {
+    await game.runToSummon([Species.EEVEE]);
+    const eevee = game.scene.getPlayerPokemon();
+
+    expect(eevee.abilityIndex).toBeGreaterThanOrEqual(0);
+    expect(eevee.abilityIndex).toBeLessThanOrEqual(2);
+  });
+});