diff --git a/test-unit/lib/displayHelper.spec.js b/test-unit/lib/displayHelper.spec.js
index 67831988..bf4d2fd1 100644
--- a/test-unit/lib/displayHelper.spec.js
+++ b/test-unit/lib/displayHelper.spec.js
@@ -1,10 +1,16 @@
 import { getNowYMD } from '~/lib/displayHelper';
 
 describe('getNowYMD', () => {
-  test('returns the formatted date in Japanese by customization', () => {
-    const mockDate = new Date('2022-01-05T12:34:56');
-    const result = getNowYMD(mockDate, 'ja');
-    expect(result).toBe('2022年01月05日12時34分');
+  describe('returns the formatted date in Japanese by customization', () => {
+    test.each([
+      ['2022-01-01T00:00:00', '2022年01月01日00時00分'],
+      ['2022-01-01T01:01:01', '2022年01月01日01時01分'],
+      ['2022-12-31T23:59:59', '2022年12月31日23時59分']
+    ])('date=%p', (date, expected) => {
+      const mockDate = new Date(date);
+      const result = getNowYMD(mockDate, 'ja');
+      expect(result).toBe(expected);
+    })
   });
 
   test('returns the formatted date in English when locale is set to "en"', () => {