diff --git a/frontend/src/utils/globalHiddenColumns.test.ts b/frontend/src/utils/globalHiddenColumns.test.ts
new file mode 100644
index 00000000..a7c7c6af
--- /dev/null
+++ b/frontend/src/utils/globalHiddenColumns.test.ts
@@ -0,0 +1,27 @@
+import { describe, expect, it } from 'vitest';
+
+import {
+  filterColumnNamesByGlobalHiddenColumns,
+  normalizeGlobalHiddenColumns,
+  parseGlobalHiddenColumnsText,
+} from './globalHiddenColumns';
+
+describe('globalHiddenColumns', () => {
+  it('parses comma, semicolon, and newline separated column names with dedupe', () => {
+    expect(parseGlobalHiddenColumnsText('ID, created_by\nupdated_at；id')).toEqual([
+      'ID',
+      'created_by',
+      'updated_at',
+    ]);
+  });
+
+  it('normalizes persisted arrays and text input consistently', () => {
+    expect(normalizeGlobalHiddenColumns([' ID ', 'id', 'NAME'])).toEqual(['ID', 'NAME']);
+    expect(normalizeGlobalHiddenColumns(' ID\nNAME')).toEqual(['ID', 'NAME']);
+  });
+
+  it('filters query result columns case-insensitively', () => {
+    expect(filterColumnNamesByGlobalHiddenColumns(['ID', 'Name', 'updated_at'], ['id', 'UPDATED_AT']))
+      .toEqual(['Name']);
+  });
+});