[Bug] Lock Capsule no longer treats common items as free (#3591)

* Fixed null check to actually check for null and not 0

* Add test and `startingModifier()` override helper function

* Add tsdoc

src/modifier/modifier-type.ts

@@ -2209,7 +2209,7 @@ export function getDefaultModifierTypeForTier(tier: ModifierTier): ModifierType
 }
 
 export class ModifierTypeOption {
-  public type: ModifierType | null;
+  public type: ModifierType;
   public upgradeCount: integer;
   public cost: integer;
 

src/phases.ts

@@ -5580,7 +5580,7 @@ export class SelectModifierPhase extends BattlePhase {
     } else if (lockRarities) {
       const tierValues = [50, 125, 300, 750, 2000];
       for (const opt of typeOptions) {
-        baseValue += opt.type?.tier ? tierValues[opt.type.tier] : 0;
+        baseValue += tierValues[opt.type.tier ?? 0];
       }
     } else {
       baseValue = 250;

src/test/items/lock_capsule.test.ts

@@ -0,0 +1,47 @@
+import GameManager from "#test/utils/gameManager";
+import Phase from "phaser";
+import { afterEach, beforeAll, beforeEach, describe, expect, it } from "vitest";
+import { Abilities } from "#app/enums/abilities.js";
+import { Moves } from "#app/enums/moves.js";
+import { getMovePosition } from "../utils/gameManagerUtils";
+import { SelectModifierPhase } from "#app/phases.js";
+import { ModifierTypeOption, modifierTypes } from "#app/modifier/modifier-type.js";
+
+describe("Items - Lock Capsule", () => {
+  let phaserGame: Phaser.Game;
+  let game: GameManager;
+
+  beforeAll(() => {
+    phaserGame = new Phase.Game({
+      type: Phaser.HEADLESS,
+    });
+  });
+
+  afterEach(() => {
+    game.phaseInterceptor.restoreOg();
+  });
+
+  beforeEach(() => {
+    game = new GameManager(phaserGame);
+
+    game.override
+      .battleType("single")
+      .startingLevel(200)
+      .moveset([Moves.SURF])
+      .enemyAbility(Abilities.BALL_FETCH)
+      .startingModifier([{name: "LOCK_CAPSULE"}]);
+  });
+
+  it("doesn't set the cost of common tier items to 0", async() => {
+    await game.startBattle();
+
+    game.doAttack(getMovePosition(game.scene, 0, Moves.SURF));
+    await game.phaseInterceptor.to(SelectModifierPhase, false);
+
+    const rewards = game.scene.getCurrentPhase() as SelectModifierPhase;
+    const potion = new ModifierTypeOption(modifierTypes.POTION(), 0, 40); // Common tier item
+    const rerollCost = rewards.getRerollCost([potion, potion, potion], true);
+
+    expect(rerollCost).toBe(150);
+  }, 20000);
+});

src/test/utils/helpers/overridesHelper.ts

@@ -84,6 +84,17 @@ export class OverridesHelper extends GameManagerHelper {
     return this;
   }
 
+  /**
+   * Override the player's starting modifiers
+   * @param modifiers the modifiers to set
+   * @returns this
+   */
+  startingModifier(modifiers: ModifierOverride[]): this {
+    vi.spyOn(Overrides, "STARTING_MODIFIER_OVERRIDE", "get").mockReturnValue(modifiers);
+    this.log(`Player starting modifiers set to: ${modifiers}`);
+    return this;
+  }
+
   /**
    * Override the player (pokemon) {@linkcode Abilities | ability}
    * @param ability the (pokemon) {@linkcode Abilities | ability} to set