diff --git a/app/actions/local/reactions.test.ts b/app/actions/local/reactions.test.ts
new file mode 100644
index 000000000..ff08b5f52
--- /dev/null
+++ b/app/actions/local/reactions.test.ts
@@ -0,0 +1,129 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+import DatabaseManager from '@database/manager';
+import * as recentReactionsQueries from '@queries/servers/system';
+import * as emojiHelpers from '@utils/emoji/helpers';
+import * as logUtils from '@utils/log';
+
+import {addRecentReaction} from './reactions';
+
+import type ServerDataOperator from '@app/database/operator/server_data_operator';
+
+jest.mock('@database/manager');
+jest.mock('@queries/servers/system');
+jest.mock('@utils/emoji/helpers');
+jest.mock('@utils/log');
+
+describe('addRecentReaction', () => {
+    let operator: ServerDataOperator;
+    const serverUrl = 'baseHandler.test.com';
+
+    beforeEach(async () => {
+        jest.clearAllMocks();
+
+        await DatabaseManager.init([serverUrl]);
+        operator = DatabaseManager.serverDatabases[serverUrl]!.operator;
+
+        (recentReactionsQueries.getRecentReactions as jest.Mock).mockResolvedValue([]);
+        (emojiHelpers.getEmojiFirstAlias as jest.Mock).mockImplementation((emoji) => emoji);
+
+        operator.handleSystem = jest.fn();
+    });
+
+    afterEach(async () => {
+        await DatabaseManager.destroyServerDatabase(serverUrl);
+    });
+
+    it('should return an empty array if emojiNames is empty', async () => {
+        const result = await addRecentReaction(serverUrl, []);
+        expect(result).toEqual([]);
+    });
+
+    it('should add new emoji to the beginning of the list', async () => {
+        (recentReactionsQueries.getRecentReactions as jest.Mock).mockResolvedValue([':water:']);
+        const emojiNames = [':air:', ':fire:'];
+        await addRecentReaction(serverUrl, emojiNames);
+
+        expect(operator.handleSystem).toHaveBeenCalledWith({
+            systems: [{
+                id: 'recentReactions',
+                value: JSON.stringify([':fire:', ':air:', ':water:']),
+            }],
+            prepareRecordsOnly: false,
+        });
+    });
+
+    it('should move existing emoji to the beginning of the list', async () => {
+        (recentReactionsQueries.getRecentReactions as jest.Mock).mockResolvedValue([':water:', ':fire:']);
+        const emojiNames = [':air:', ':fire:'];
+        await addRecentReaction(serverUrl, emojiNames);
+
+        expect(operator.handleSystem).toHaveBeenCalledWith({
+            systems: [{
+                id: 'recentReactions',
+                value: JSON.stringify([':fire:', ':air:', ':water:']),
+            }],
+            prepareRecordsOnly: false,
+        });
+    });
+
+    it('should limit the list to MAXIMUM_RECENT_EMOJI', async () => {
+        const longEmojiList = Array.from({length: 40}, (_, i) => `emoji${i}`);
+        (recentReactionsQueries.getRecentReactions as jest.Mock).mockResolvedValue(longEmojiList);
+        await addRecentReaction(serverUrl, ['newEmoji']);
+
+        const handleSystemCall = (operator.handleSystem as jest.Mock).mock.calls[0][0];
+        const savedEmojis = JSON.parse(handleSystemCall.systems[0].value);
+        expect(savedEmojis.length).toBe(27);
+        expect(savedEmojis[0]).toBe('newEmoji');
+    });
+
+    it('should use getEmojiFirstAlias for each emoji', async () => {
+        (emojiHelpers.getEmojiFirstAlias as jest.Mock).mockImplementation((emoji) => {
+            if (emoji === ':air:') {
+                return ':wind:';
+            }
+            if (emoji === ':fire:') {
+                return ':flame:';
+            }
+            return emoji;
+        });
+
+        const emojiNames = [':air:', ':fire:'];
+        await addRecentReaction(serverUrl, emojiNames);
+
+        expect(emojiHelpers.getEmojiFirstAlias).toHaveBeenCalledTimes(2);
+        expect(emojiHelpers.getEmojiFirstAlias).toHaveBeenCalledWith(':air:');
+        expect(emojiHelpers.getEmojiFirstAlias).toHaveBeenCalledWith(':fire:');
+        expect(operator.handleSystem).toHaveBeenCalledWith({
+            systems: [{
+                id: 'recentReactions',
+                value: JSON.stringify([':flame:', ':wind:']),
+            }],
+            prepareRecordsOnly: false,
+        });
+    });
+
+    it('should handle errors and log them', async () => {
+        const unregisteredServerUrl = 'unregistered.test.com';
+        const failedError = new Error(`${unregisteredServerUrl} database not found`);
+
+        const result = await addRecentReaction(unregisteredServerUrl, [':air:']);
+
+        expect(logUtils.logError).toHaveBeenCalledWith('Failed addRecentReaction', failedError);
+        expect(result).toEqual({error: failedError});
+    });
+
+    it('should handle prepareRecordsOnly=true flag', async () => {
+        const emojiNames = [':air:'];
+        await addRecentReaction(serverUrl, emojiNames, true);
+
+        expect(operator.handleSystem).toHaveBeenCalledWith({
+            systems: [{
+                id: 'recentReactions',
+                value: JSON.stringify([':air:']),
+            }],
+            prepareRecordsOnly: true,
+        });
+    });
+});