diff --git a/src/pages/stock/components/PortfolioTab.jsx b/src/pages/stock/components/PortfolioTab.jsx
index 2104fad..9582799 100644
--- a/src/pages/stock/components/PortfolioTab.jsx
+++ b/src/pages/stock/components/PortfolioTab.jsx
@@ -5,26 +5,7 @@ import {
     Tooltip as ChartTooltip,
 } from 'recharts';
 import { formatNumber, formatPercent, toNumeric, profitColorClass, numFitClass } from '../stockUtils';
-
-const formatPriceTime = (iso) => {
-    if (!iso) return '';
-    const d = new Date(iso);
-    if (Number.isNaN(d.getTime())) return '';
-    return `${String(d.getHours()).padStart(2, '0')}:${String(d.getMinutes()).padStart(2, '0')}`;
-};
-
-const PriceSessionBadge = ({ session, asOf }) => {
-    if (session !== 'NXT_AFTER' && session !== 'NXT_PRE') return null;
-    const isPre = session === 'NXT_PRE';
-    const label = isPre ? 'NXT 프리' : 'NXT';
-    const desc = isPre ? 'NXT 프리마켓 거래가' : 'NXT 야간거래 (15:30~20:00)';
-    const time = formatPriceTime(asOf);
-    return (
-        <span className="pf-nxt-badge" title={time ? `${desc} · ${time}` : desc}>
-            {label}
-        </span>
-    );
-};
+import PriceSessionBadge from './portfolio/PriceSessionBadge';
 
 const PortfolioTab = ({ pf, asset, handleSell, handleSaveSnapshot }) => (
     <>
diff --git a/src/pages/stock/components/portfolio/PriceSessionBadge.jsx b/src/pages/stock/components/portfolio/PriceSessionBadge.jsx
new file mode 100644
index 0000000..390fbd3
--- /dev/null
+++ b/src/pages/stock/components/portfolio/PriceSessionBadge.jsx
@@ -0,0 +1,17 @@
+import React from 'react';
+import { formatPriceTime } from './portfolioUtils';
+
+const PriceSessionBadge = ({ session, asOf }) => {
+    if (session !== 'NXT_AFTER' && session !== 'NXT_PRE') return null;
+    const isPre = session === 'NXT_PRE';
+    const label = isPre ? 'NXT 프리' : 'NXT';
+    const desc = isPre ? 'NXT 프리마켓 거래가' : 'NXT 야간거래 (15:30~20:00)';
+    const time = formatPriceTime(asOf);
+    return (
+        <span className="pf-nxt-badge" title={time ? `${desc} · ${time}` : desc}>
+            {label}
+        </span>
+    );
+};
+
+export default PriceSessionBadge;
diff --git a/src/pages/stock/components/portfolio/PriceSessionBadge.test.jsx b/src/pages/stock/components/portfolio/PriceSessionBadge.test.jsx
new file mode 100644
index 0000000..b31ca89
--- /dev/null
+++ b/src/pages/stock/components/portfolio/PriceSessionBadge.test.jsx
@@ -0,0 +1,17 @@
+import { describe, it, expect } from 'vitest';
+import { render, screen } from '@testing-library/react';
+import PriceSessionBadge from './PriceSessionBadge.jsx';
+
+describe('PriceSessionBadge', () => {
+  it('NXT_AFTER → "NXT", NXT_PRE → "NXT 프리"', () => {
+    const { unmount } = render(<PriceSessionBadge session="NXT_AFTER" />);
+    expect(screen.getByText('NXT')).toBeInTheDocument();
+    unmount();
+    render(<PriceSessionBadge session="NXT_PRE" />);
+    expect(screen.getByText('NXT 프리')).toBeInTheDocument();
+  });
+  it('그 외 세션 → 렌더 없음', () => {
+    const { container } = render(<PriceSessionBadge session="REGULAR" />);
+    expect(container).toBeEmptyDOMElement();
+  });
+});
diff --git a/src/pages/stock/components/portfolio/portfolioUtils.js b/src/pages/stock/components/portfolio/portfolioUtils.js
new file mode 100644
index 0000000..414d01a
--- /dev/null
+++ b/src/pages/stock/components/portfolio/portfolioUtils.js
@@ -0,0 +1,6 @@
+export const formatPriceTime = (iso) => {
+    if (!iso) return '';
+    const d = new Date(iso);
+    if (Number.isNaN(d.getTime())) return '';
+    return `${String(d.getHours()).padStart(2, '0')}:${String(d.getMinutes()).padStart(2, '0')}`;
+};
diff --git a/src/pages/stock/components/portfolio/portfolioUtils.test.js b/src/pages/stock/components/portfolio/portfolioUtils.test.js
new file mode 100644
index 0000000..f9ae276
--- /dev/null
+++ b/src/pages/stock/components/portfolio/portfolioUtils.test.js
@@ -0,0 +1,14 @@
+import { describe, it, expect } from 'vitest';
+import { formatPriceTime } from './portfolioUtils.js';
+
+describe('formatPriceTime', () => {
+  it('유효 ISO → HH:MM (제로패드)', () => {
+    expect(formatPriceTime('2026-07-10T09:05:00')).toBe('09:05');
+    expect(formatPriceTime('2026-07-10T18:30:00')).toBe('18:30');
+  });
+  it('falsy/invalid → 빈 문자열', () => {
+    expect(formatPriceTime('')).toBe('');
+    expect(formatPriceTime(null)).toBe('');
+    expect(formatPriceTime('not-a-date')).toBe('');
+  });
+});