diff --git a/docs/gamification-server-plan.md b/docs/gamification-server-plan.md
index 8341c2c..6f6e85c 100644
--- a/docs/gamification-server-plan.md
+++ b/docs/gamification-server-plan.md
@@ -78,7 +78,7 @@
 | G3-4 | 实现商店商品和购买接口 | [x] | 商品价格符合设计：提示羽毛 80、爱心补给 150、双倍 XP 250、连胜护盾 400、装扮 800-3000 |
 | G3-5 | 实现道具使用接口 | [x] | 爱心补给恢复满心，双倍 XP 药水 15 分钟生效，提示羽毛返回可排除选项，连胜护盾可保护断签 |
 | G3-6 | 更新 bootstrap/shop DTO | [x] | 客户端能拿到金币、库存、可购买商品、广告商品、订阅权益 |
-| G3-7 | 添加金币/商店测试 | [ ] | 覆盖余额不足、重复购买、使用道具、药水时效、库存扣减和流水记录 |
+| G3-7 | 添加金币/商店测试 | [x] | 覆盖余额不足、重复购买、使用道具、药水时效、库存扣减和流水记录 |
 
 验证记录（2026-05-13）：G3-1 已通过 `./node_modules/.bin/tsc --noEmit`、`./node_modules/.bin/eslint .` 和 `git diff --check`；定向运行 `./node_modules/.bin/vitest run src/__tests__/services/gamification/coin-service.test.ts src/__tests__/services/learning/challenge-service.test.ts` 仍在启动阶段被 `@rolldown/binding-darwin-x64` 原生 binding 未签名问题阻塞。
 验证记录（2026-05-13）：G3-2 已通过 `./node_modules/.bin/tsc --noEmit`、`./node_modules/.bin/eslint .` 和 `git diff --check`；定向运行 `./node_modules/.bin/vitest run src/__tests__/services/gamification/chest-service.test.ts src/__tests__/services/gamification/coin-service.test.ts src/__tests__/services/gamification-rules.test.ts` 仍在启动阶段被同一个 `@rolldown/binding-darwin-x64` 原生 binding 未签名问题阻塞。
@@ -86,6 +86,7 @@
 验证记录（2026-05-13）：G3-4 已通过 `./node_modules/.bin/tsc --noEmit`、`./node_modules/.bin/eslint .` 和 `git diff --check`；定向运行 `./node_modules/.bin/vitest run src/__tests__/services/shop/shop-service.test.ts src/__tests__/services/gamification/coin-service.test.ts src/__tests__/services/gamification/inventory-service.test.ts` 仍在启动阶段被同一个 `@rolldown/binding-darwin-x64` 原生 binding 未签名问题阻塞。
 验证记录（2026-05-13）：G3-5 已通过 `./node_modules/.bin/tsc --noEmit`、`./node_modules/.bin/eslint .` 和 `git diff --check`；定向运行 `./node_modules/.bin/vitest run src/__tests__/services/gamification/item-use-service.test.ts src/__tests__/services/gamification/inventory-service.test.ts` 仍在启动阶段被同一个 `@rolldown/binding-darwin-x64` 原生 binding 未签名问题阻塞。
 验证记录（2026-05-13）：G3-6 已通过 `./node_modules/.bin/tsc --noEmit`、`./node_modules/.bin/eslint .` 和 `git diff --check`；定向运行 `./node_modules/.bin/vitest run src/__tests__/services/app/bootstrap-service.test.ts src/__tests__/services/gamification/inventory-service.test.ts src/__tests__/services/shop/shop-service.test.ts` 仍在启动阶段被同一个 `@rolldown/binding-darwin-x64` 原生 binding 未签名问题阻塞。
+验证记录（2026-05-13）：G3-7 已通过 `./node_modules/.bin/tsc --noEmit`、`./node_modules/.bin/eslint .` 和 `git diff --check`；定向运行 `./node_modules/.bin/vitest run src/__tests__/services/gamification/coin-service.test.ts src/__tests__/services/shop/shop-service.test.ts src/__tests__/services/gamification/inventory-service.test.ts src/__tests__/services/gamification/item-use-service.test.ts` 仍在启动阶段被同一个 `@rolldown/binding-darwin-x64` 原生 binding 未签名问题阻塞。
 
 ## Phase G4：广告恢复与订阅权益对齐
 
diff --git a/src/__tests__/services/gamification/item-use-service.test.ts b/src/__tests__/services/gamification/item-use-service.test.ts
index f4946a5..636e447 100644
--- a/src/__tests__/services/gamification/item-use-service.test.ts
+++ b/src/__tests__/services/gamification/item-use-service.test.ts
@@ -89,10 +89,13 @@ describe('item-use-service', () => {
       clientRequestId: 'use-xp-1',
     });
 
+    const activeUntilMs = Date.parse(result.effect.activeUntil ?? '');
+    const expectedMs = Date.now() + 15 * 60 * 1000;
     expect(result.itemId).toBe('double_xp_potion');
     expect(result.quantityRemaining).toBe(0);
     expect(result.effect.type).toBe('double_xp');
     expect(result.effect.activeUntil).toEqual(expect.any(String));
+    expect(Math.abs(activeUntilMs - expectedMs)).toBeLessThan(2_000);
     expect(updateSet).toHaveBeenCalledWith(expect.objectContaining({
       activeUntil: expect.any(Date),
       metadata: {
diff --git a/src/__tests__/services/shop/shop-service.test.ts b/src/__tests__/services/shop/shop-service.test.ts
index 5ea0d71..eefdcfa 100644
--- a/src/__tests__/services/shop/shop-service.test.ts
+++ b/src/__tests__/services/shop/shop-service.test.ts
@@ -106,6 +106,29 @@ describe('shop-service', () => {
     }));
   });
 
+  it('does not spend coins or grant inventory twice for duplicate purchases', async () => {
+    mockSelectQueue([
+      [{ id: 'coin-tx-1' }], // spendCoins: existing spend transaction
+      [{ coinsBalance: 220 }],
+      [{ id: 'item-tx-1' }], // grantInventoryItem: existing item grant
+      [{ itemId: 'hint_feather', quantity: 1, activeUntil: null, metadata: null }],
+    ]);
+
+    const result = await purchaseShopProduct('user-1', 'hint-feather', 'request-1');
+
+    expect(result.product.id).toBe('hint-feather');
+    expect(result.coinsSpent).toBe(0);
+    expect(result.coinsBalance).toBe(220);
+    expect(result.item).toEqual({
+      itemId: 'hint_feather',
+      quantity: 1,
+      activeUntil: null,
+      metadata: null,
+    });
+    expect(db.insert).not.toHaveBeenCalled();
+    expect(db.update).not.toHaveBeenCalled();
+  });
+
   it('throws when the user does not have enough coins', async () => {
     mockSelectQueue([
       [], // no existing spend