fix(wallet): 丢弃切换账号后返回的旧余额响应

test/commerce/wallet_identity_test.dart

@@ -0,0 +1,84 @@
+// Author: fruit.com.cn
+// 验证登出、切换请求及销毁后不会回写旧钱包。
+
+import 'dart:async';
+
+import 'package:flutter_test/flutter_test.dart';
+import 'package:fruitshorts/core/data/models/wallet.dart';
+import 'package:fruitshorts/core/data/repositories/commerce_repository.dart';
+import 'package:fruitshorts/core/data/services/wallet_controller.dart';
+
+const _oldBalance = 320;
+const _newBalance = 50;
+
+void main() {
+  test('should_discard_inflight_balance_when_identity_is_reset', () async {
+    final repository = _PendingCommerce();
+    final wallet = WalletController(repository);
+    final pending = wallet.load();
+
+    wallet.reset();
+    repository.requests.single.complete(_snapshot(_oldBalance));
+    await pending;
+
+    expect(wallet.snapshot, isNull);
+    expect(wallet.loading, isFalse);
+    wallet.dispose();
+  });
+
+  test('should_keep_new_balance_when_an_older_request_finishes_last', () async {
+    final repository = _PendingCommerce();
+    final wallet = WalletController(repository);
+    final oldRequest = wallet.load();
+    wallet.reset();
+    final newRequest = wallet.load();
+
+    repository.requests.last.complete(_snapshot(_newBalance));
+    await newRequest;
+    repository.requests.first.complete(_snapshot(_oldBalance));
+    await oldRequest;
+
+    expect(wallet.balance, _newBalance);
+    expect(wallet.loading, isFalse);
+    wallet.dispose();
+  });
+
+  test('should_discard_inflight_error_when_wallet_is_reset', () async {
+    final repository = _PendingCommerce();
+    final wallet = WalletController(repository);
+    final pending = wallet.load();
+
+    wallet.reset();
+    repository.requests.single.completeError(StateError('old request'));
+    await pending;
+
+    expect(wallet.error, isNull);
+    expect(wallet.snapshot, isNull);
+    wallet.dispose();
+  });
+}
+
+WalletSnapshot _snapshot(int balance) => WalletSnapshot(
+  wallet: CoinWallet(
+    coinBalance: balance,
+    totalRechargedCoin: balance,
+    totalConsumedCoin: 0,
+    totalRefundedCoin: 0,
+  ),
+);
+
+class _PendingCommerce implements CommerceRepository {
+  final requests = <Completer<WalletSnapshot>>[];
+
+  @override
+  Future<WalletSnapshot> fetchWallet() {
+    final request = Completer<WalletSnapshot>();
+    requests.add(request);
+    return request.future;
+  }
+
+  @override
+  Future<UnlockResult> unlock(String episodeId) async {
+    throw UnimplementedError('not needed by wallet identity tests');
+  }
+}