diff --git a/web/utils/typeahead-utils.test.js b/web/utils/typeahead-utils.test.js
index 984dba026..d9a3962c1 100644
--- a/web/utils/typeahead-utils.test.js
+++ b/web/utils/typeahead-utils.test.js
@@ -1,32 +1,100 @@
 // @flow
 
-import { getTypeaheadOverlayScroll } from './typeahead-utils.js';
+import {
+  getTypeaheadOverlayScroll,
+  webMentionTypeaheadRegex,
+} from './typeahead-utils.js';
 import { typeaheadStyle } from '../chat/chat-constants.js';
 
 describe('getTypeaheadOverlayScroll', () => {
   it(
     'should return the same scroll position when' +
       'it is already scrolled to the top and changing between 2nd button',
     () => expect(getTypeaheadOverlayScroll(0, 1)).toEqual(0),
   );
 
   it(
     'should scroll down when it is scrolled to the top' +
       'and changing to button out of screen',
     () =>
       expect(getTypeaheadOverlayScroll(0, 6)).toEqual(
         (6 + 1) * typeaheadStyle.rowHeight +
           typeaheadStyle.tooltipVerticalPadding -
           typeaheadStyle.tooltipMaxHeight,
       ),
   );
 
   it(
     'should scroll up when it is scrolled somewhere down' +
       'and changing to button out of screen to the top',
     () =>
       expect(getTypeaheadOverlayScroll(500, 3)).toEqual(
         3 * typeaheadStyle.rowHeight,
       ),
   );
 });
+
+describe('webMentionTypeaheadRegex', () => {
+  const validMatches = [
+    {
+      textPrefix: '',
+      mentionText: 'mention123',
+    },
+    {
+      textPrefix: '',
+      mentionText: 'mention with space',
+    },
+    {
+      textPrefix: 'text prefix ',
+      mentionText: 'mention with space',
+    },
+    {
+      textPrefix: 'This is a test ',
+      mentionText: 'mention',
+    },
+    {
+      textPrefix: '',
+      mentionText: '',
+    },
+    {
+      textPrefix: 'A multi-line\nmention with\nnewlines ',
+      mentionText: 'mention',
+    },
+    {
+      textPrefix: 'text @first mention ',
+      mentionText: 'second mention',
+    },
+    {
+      textPrefix: 'text text \n@first \n',
+      mentionText: 'second mention',
+    },
+  ];
+
+  it('should match webMentionTypeaheadRegex', () =>
+    validMatches.forEach(validMatchObject => {
+      const text = `${validMatchObject.textPrefix}@${validMatchObject.mentionText}`;
+      const match = text.match(webMentionTypeaheadRegex);
+      expect(match).toBeTruthy();
+      expect(match?.groups?.textPrefix ?? '').toEqual(
+        validMatchObject.textPrefix,
+      );
+      expect(match?.groups?.mentionText ?? '').toEqual(
+        validMatchObject.mentionText,
+      );
+    }));
+
+  const invalidMatches = [
+    'This is not a valid text with mention',
+    `@${'a'.repeat(200)} `,
+    'text prefix\\@mention',
+    '@mention\nnewline \\@mention with space',
+    '\\@',
+    '\\@username',
+    '\\@thread with spaces',
+  ];
+
+  it('should not match webMentionTypeaheadRegex', () =>
+    invalidMatches.forEach(text =>
+      expect(text.match(webMentionTypeaheadRegex)).toBeFalsy(),
+    ));
+});