[Balance] Add faint trigger to various form changes (#6122)

* [Balance] Add faint trigger to Battle Bond Greninja's form change

The form change functionality will now be slightly closer to Generation 7/8, as the Greninja will now revert from Ash form to Battle Bond form upon fainting.

* Change how the form change on faint is triggered

It is no longer directly handled by the faint phase, and is instead part of the abilities now, as more than Battle Bond Greninja revert via this method (Disguise Mimikyu, Power Construct Zygarde).

* Adjust Disguise test

src/data/abilities/ability.ts

@@ -5305,6 +5305,26 @@ export class PostFaintUnsuppressedWeatherFormChangeAbAttr extends PostFaintAbAtt
   }
 }
 
+export class PostFaintFormChangeAbAttr extends PostFaintAbAttr {
+  private formFunc: (p: Pokemon) => number;
+
+  constructor(formFunc: (p: Pokemon) => number) {
+    super(true);
+
+    this.formFunc = formFunc;
+  }
+
+  override canApply({ pokemon }: AbAttrBaseParams): boolean {
+    return this.formFunc(pokemon) !== pokemon.formIndex;
+  }
+
+  override apply({ pokemon, simulated }: AbAttrBaseParams): void {
+    if (!simulated) {
+      globalScene.triggerPokemonFormChange(pokemon, SpeciesFormChangeAbilityTrigger, false);
+    }
+  }
+}
+
 export class PostFaintContactDamageAbAttr extends PostFaintAbAttr {
   private damageRatio: number;
 
@@ -7296,6 +7316,7 @@ export function initAbilities() {
         (pokemon, abilityName) => i18next.t("abilityTriggers:disguiseAvoidedDamage", { pokemonNameWithAffix: getPokemonNameWithAffix(pokemon), abilityName: abilityName }),
         (pokemon) => toDmgValue(pokemon.getMaxHp() / 8))
       .attr(PostBattleInitFormChangeAbAttr, () => 0)
+      .attr(PostFaintFormChangeAbAttr, () => 0)
       .uncopiable()
       .unreplaceable()
       .unsuppressable()
@@ -7304,6 +7325,7 @@ export function initAbilities() {
     new Ability(AbilityId.BATTLE_BOND, 7)
       .attr(PostVictoryFormChangeAbAttr, () => 2)
       .attr(PostBattleInitFormChangeAbAttr, () => 1)
+      .attr(PostFaintFormChangeAbAttr, () => 1)
       .attr(NoFusionAbilityAbAttr)
       .uncopiable()
       .unreplaceable()
@@ -7315,6 +7337,7 @@ export function initAbilities() {
       .conditionalAttr(p => p.formIndex === 4 || p.formIndex === 5, PostBattleInitFormChangeAbAttr, p => p.formIndex - 2)
       .conditionalAttr(p => p.getHpRatio() <= 0.5 && (p.formIndex === 2 || p.formIndex === 3), PostSummonFormChangeAbAttr, p => p.formIndex + 2)
       .conditionalAttr(p => p.getHpRatio() <= 0.5 && (p.formIndex === 2 || p.formIndex === 3), PostTurnFormChangeAbAttr, p => p.formIndex + 2)
+      .conditionalAttr(p => p.formIndex === 4 || p.formIndex === 5, PostFaintFormChangeAbAttr, p => p.formIndex - 2)
       .attr(NoFusionAbilityAbAttr)
       .uncopiable()
       .unreplaceable()

test/abilities/disguise.test.ts

@@ -165,7 +165,7 @@ describe("Abilities - Disguise", () => {
     expect(mimikyu.formIndex).toBe(disguisedForm);
   });
 
-  it("reverts to Disguised form on biome change when fainted", async () => {
+  it("reverts to Disguised form when fainted", async () => {
     game.override
       .startingWave(10)
       .starterSpecies(0)
@@ -181,10 +181,6 @@ describe("Abilities - Disguise", () => {
 
     game.move.select(MoveId.SPLASH);
     await game.killPokemon(mimikyu1);
-    game.doSelectPartyPokemon(1);
-    await game.toNextTurn();
-    game.move.select(MoveId.SPLASH);
-    await game.doKillOpponents();
     await game.phaseInterceptor.to("QuietFormChangePhase");
 
     expect(mimikyu1.formIndex).toBe(disguisedForm);