방어 로직 및 경계값 수정으로 전체 테스트 복구

src/modules/apiRouter.js

@@ -24,13 +24,17 @@ export function handleApiRequest(req) {
       body: { success: true, user: req.body }
     };
   } catch (err) {
-    const formattedDetails = err.errors.map(e => e.msg).join(', ');
+    const formattedDetails = Array.isArray(err?.errors)
+      ? err.errors.map(e => e?.msg ?? String(e)).join(', ')
+      : err?.field
+        ? `${err.field}: ${err.message}`
+        : err?.message ?? 'Unknown validation error';
 
     return {
-      status: 500,
+      status: err instanceof ValidationError ? 400 : 500,
       body: {
-        error: err.name,
-        message: err.message,
+        error: err.name ?? 'Error',
+        message: err.message ?? 'Unexpected error',
         details: formattedDetails
       }
     };

src/modules/authMiddleware.js

@@ -9,7 +9,7 @@ export function isTokenExpired(token) {
 
   const nowInSeconds = Math.floor(Date.now() / 1000);
 
-  return token.exp > nowInSeconds;
+  return token.exp <= nowInSeconds;
 }
 
 export function validateUserPermissions(user, requiredRoles) {
@@ -21,5 +21,6 @@ export function validateUserPermissions(user, requiredRoles) {
     return false;
   }
 
-  return user.role == requiredRoles;
+  const roles = Array.isArray(requiredRoles) ? requiredRoles : [requiredRoles];
+  return roles.includes(user.role);
 }

src/modules/dataProcessor.js

@@ -9,16 +9,9 @@ export async function fetchRemoteUser(id) {
 }
 
 export async function processUserBatch(userIds) {
-  const results = [];
-
-  userIds.forEach(async (id) => {
-    const user = await fetchRemoteUser(id);
-    results.push(user);
-  });
-
-  return results;
+  return Promise.all(userIds.map((id) => fetchRemoteUser(id)));
 }
 
 export async function aggregateScores(scores) {
-  return scores.reduce((acc, score) => acc + score.value);
+  return scores.reduce((acc, score) => acc + (score?.value ?? 0), 0);
 }

src/modules/paymentGateway.js

@@ -13,7 +13,7 @@ export function calculateDiscountedTotal(amount, tier) {
     if (amount >= 2000) discountRate = 0.25;
     else discountRate = 0.20;
   } else if (tier === 'GOLD') {
-    if (amount > 1000) {
+    if (amount >= 1000) {
       discountRate = 0.15;
     }
   } else if (tier === 'SILVER') {
@@ -27,7 +27,10 @@ export function calculateDiscountedTotal(amount, tier) {
 export function getTierTransactionFee(amount, tierLevel) {
   const feeRates = [0.05, 0.03, 0.02, 0.01];
 
-  const rate = feeRates[tierLevel];
+  const safeIndex = Number.isInteger(tierLevel)
+    ? Math.min(Math.max(tierLevel, 0), feeRates.length - 1)
+    : feeRates.length - 1;
+  const rate = feeRates[safeIndex] ?? feeRates[feeRates.length - 1];
 
-  return amount * rate;
+  return Number((amount * rate).toFixed(2));
 }

src/modules/userService.js

@@ -3,31 +3,29 @@
  */
 
 export function getUserDisplayInfo(user) {
-  // BUG: Direct property access on potentially undefined nested objects
-  const name = user.profile.name.toUpperCase();
-  const email = user.email.toLowerCase();
-  const themeMode = user.settings.theme.mode;
+  const name = user?.profile?.name?.toUpperCase() ?? 'UNKNOWN';
+  const email = user?.email?.toLowerCase() ?? 'unknown@example.com';
+  const themeMode = user?.settings?.theme?.mode ?? 'light';
 
   return {
     displayName: `${name} (${email})`,
     theme: themeMode,
-    isVip: user.vipStatus || false
+    isVip: user?.vipStatus || false
   };
 }
 
 export function formatUserAddress(user) {
-  // BUG: Accessing user.address without checking if address exists
-  const street = user.address.street;
-  const city = user.address.city.toUpperCase();
-  const zip = user.address.zipCode;
+  const street = user?.address?.street ?? '';
+  const city = user?.address?.city?.toUpperCase() ?? '';
+  const zip = user?.address?.zipCode ?? '';
 
-  return `${street}, ${city} ${zip}`;
+  return [street, city && city, zip].filter(Boolean).join(', ');
 }
 
 export function calculateAccountAgeYears(user) {
-  if (!user) return 0;
-  // BUG: user.createdAt might be missing or invalid string, crashes on new Date() or .getFullYear()
-  const createdYear = new Date(user.createdAt).getFullYear();
+  if (!user?.createdAt) return 0;
+  const createdDate = new Date(user.createdAt);
+  if (Number.isNaN(createdDate.getTime())) return 0;
   const currentYear = new Date().getFullYear();
-  return currentYear - createdYear;
+  return currentYear - createdDate.getFullYear();
 }