diff --git a/app/hooks/android_back_handler.test.ts b/app/hooks/android_back_handler.test.ts
new file mode 100644
index 0000000000..a2dc79e8aa
--- /dev/null
+++ b/app/hooks/android_back_handler.test.ts
@@ -0,0 +1,60 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+import {renderHook} from '@testing-library/react-hooks';
+import {BackHandler} from 'react-native';
+
+import NavigationStore from '@store/navigation_store';
+
+import useAndroidHardwareBackHandler from './android_back_handler';
+
+jest.mock('react-native', () => ({
+    BackHandler: {
+        addEventListener: jest.fn(),
+    },
+}));
+
+jest.mock('@store/navigation_store', () => ({
+    getVisibleScreen: jest.fn(),
+}));
+
+test('useAndroidHardwareBackHandler - calls callback when visible screen matches componentId', () => {
+    const componentId = 'About';
+    const callback = jest.fn();
+
+    (NavigationStore.getVisibleScreen as jest.Mock).mockReturnValue(componentId);
+
+    renderHook(() => useAndroidHardwareBackHandler(componentId, callback));
+
+    const hardwareBackPressHandler = (BackHandler.addEventListener as jest.Mock).mock.calls[0][1];
+    hardwareBackPressHandler();
+
+    expect(callback).toHaveBeenCalled();
+});
+
+test('useAndroidHardwareBackHandler - does not call callback when visible screen does not match componentId', () => {
+    const componentId = 'About';
+    const callback = jest.fn();
+
+    (NavigationStore.getVisibleScreen as jest.Mock).mockReturnValue('otherScreen');
+
+    renderHook(() => useAndroidHardwareBackHandler(componentId, callback));
+
+    const hardwareBackPressHandler = (BackHandler.addEventListener as jest.Mock).mock.calls[0][1];
+    hardwareBackPressHandler();
+
+    expect(callback).not.toHaveBeenCalled();
+});
+
+test('useAndroidHardwareBackHandler - removes event listener on unmount', () => {
+    const componentId = 'About';
+    const callback = jest.fn();
+    const remove = jest.fn();
+    (BackHandler.addEventListener as jest.Mock).mockReturnValue({remove});
+
+    const {unmount} = renderHook(() => useAndroidHardwareBackHandler(componentId, callback));
+
+    unmount();
+
+    expect(remove).toHaveBeenCalled();
+});
diff --git a/app/hooks/emoji_category_bar.test.ts b/app/hooks/emoji_category_bar.test.ts
new file mode 100644
index 0000000000..8b599083b6
--- /dev/null
+++ b/app/hooks/emoji_category_bar.test.ts
@@ -0,0 +1,128 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+import {renderHook, act} from '@testing-library/react-hooks';
+import {BehaviorSubject} from 'rxjs';
+
+import {
+    selectEmojiCategoryBarSection,
+    setEmojiCategoryBarSection,
+    setEmojiCategoryBarIcons,
+    setEmojiSkinTone,
+    useEmojiCategoryBar,
+    useEmojiSkinTone,
+} from './emoji_category_bar';
+
+describe('EmojiCategoryBar', () => {
+    const mockSubject = {
+        next: jest.fn(),
+        value: {
+            icons: undefined,
+            currentIndex: 0,
+            selectedIndex: undefined,
+            skinTone: 'default',
+        },
+        subscribe: jest.fn().mockImplementation((callback) => {
+            callback(mockSubject.value);
+            return {unsubscribe: jest.fn()};
+        }),
+    };
+
+    beforeEach(() => {
+        jest.spyOn(BehaviorSubject.prototype, 'next').mockImplementation(mockSubject.next);
+        jest.spyOn(BehaviorSubject.prototype, 'subscribe').mockImplementation(mockSubject.subscribe);
+        jest.spyOn(BehaviorSubject.prototype, 'value', 'get').mockReturnValue(mockSubject.value);
+    });
+
+    afterEach(() => {
+        jest.clearAllMocks();
+    });
+
+    describe('setEmojiSkinTone', () => {
+        it('should update the skin tone in the state', () => {
+            setEmojiSkinTone('light');
+
+            expect(mockSubject.next).toHaveBeenCalledWith({
+                ...mockSubject.value,
+                skinTone: 'light',
+            });
+        });
+    });
+
+    describe('useEmojiSkinTone', () => {
+        it('should return the current skin tone', () => {
+            const {result} = renderHook(() => useEmojiSkinTone());
+
+            expect(result.current).toBe('default');
+        });
+
+        it('should update the skin tone when it changes', () => {
+            const {result} = renderHook(() => useEmojiSkinTone());
+
+            act(() => {
+                mockSubject.subscribe.mock.calls[0][0]({skinTone: 'dark'});
+            });
+
+            expect(result.current).toBe('dark');
+        });
+    });
+
+    describe('selectEmojiCategoryBarSection', () => {
+        it('should update the selected index in the state', () => {
+            selectEmojiCategoryBarSection(1);
+
+            expect(mockSubject.next).toHaveBeenCalledWith({
+                ...mockSubject.value,
+                selectedIndex: 1,
+            });
+        });
+    });
+
+    describe('setEmojiCategoryBarSection', () => {
+        it('should update the current index in the state', () => {
+            setEmojiCategoryBarSection(1);
+
+            expect(mockSubject.next).toHaveBeenCalledWith({
+                ...mockSubject.value,
+                currentIndex: 1,
+            });
+        });
+    });
+
+    describe('setEmojiCategoryBarIcons', () => {
+        it('should update the icons in the state', () => {
+            const icons = [{key: 'smile', name: 'smile', icon: 'smile'}];
+            setEmojiCategoryBarIcons(icons);
+
+            expect(mockSubject.next).toHaveBeenCalledWith({
+                ...mockSubject.value,
+                icons,
+            });
+        });
+    });
+
+    describe('useEmojiCategoryBar', () => {
+        it('should return the current state', () => {
+            const {result} = renderHook(() => useEmojiCategoryBar());
+
+            expect(result.current).toEqual(mockSubject.value);
+        });
+
+        it('should update the state when it changes', () => {
+            const {result} = renderHook(() => useEmojiCategoryBar());
+
+            const newState = {
+                icons: [{name: 'smile', icon: 'smile'}],
+                currentIndex: 1,
+                selectedIndex: 2,
+                skinTone: 'dark',
+            };
+
+            act(() => {
+                mockSubject.subscribe.mock.calls[0][0](newState);
+            });
+
+            expect(result.current).toEqual(newState);
+        });
+    });
+});
diff --git a/app/hooks/files.test.ts b/app/hooks/files.test.ts
index 980a3b3716..f4b2e0c9d3 100644
--- a/app/hooks/files.test.ts
+++ b/app/hooks/files.test.ts
@@ -3,12 +3,16 @@
 
 import {renderHook} from '@testing-library/react-hooks';
 
+import {getLocalFileInfo} from '@actions/local/file';
 import {buildFilePreviewUrl, buildFileUrl} from '@actions/remote/file';
 import {useServerUrl} from '@context/server';
 import {mockFileInfo} from '@test/api_mocks/file';
 import {isGif, isImage, isVideo} from '@utils/file';
+import {getImageSize} from '@utils/gallery';
 
-import {useImageAttachments} from './files';
+import {useChannelBookmarkFiles, useImageAttachments} from './files';
+
+import type ChannelBookmarkModel from '@typings/database/models/servers/channel_bookmark';
 
 jest.mock('@actions/remote/file', () => ({
     buildFilePreviewUrl: jest.fn(),
@@ -25,6 +29,9 @@ jest.mock('@context/server', () => ({
     useServerUrl: jest.fn(),
 }));
 
+jest.mock('@utils/gallery');
+jest.mock('@actions/local/file');
+
 describe('useImageAttachments', () => {
     const serverUrl = 'https://example.com';
 
@@ -143,3 +150,42 @@ describe('useImageAttachments', () => {
         ]);
     });
 });
+
+describe('useChannelBookmarkFiles', () => {
+    it('should fetch and set file info correctly', async () => {
+        const serverUrl = 'https://example.com';
+        (useServerUrl as jest.Mock).mockReturnValue(serverUrl);
+
+        const bookmarks = [
+            {fileId: '1', ownerId: 'user1'},
+            {fileId: '2', ownerId: 'user2'},
+        ] as ChannelBookmarkModel[];
+
+        const file1 = {id: '1', localPath: 'path/to/image1', has_preview_image: true, toFileInfo: jest.fn().mockReturnValue({id: '1'})};
+        const file2 = {id: '2', localPath: 'path/to/video1', has_preview_image: false, toFileInfo: jest.fn().mockReturnValue({id: '2'})};
+
+        (getLocalFileInfo as jest.Mock).mockImplementation((url, id) => {
+            if (id === '1') {
+                return {file: file1};
+            } else if (id === '2') {
+                return {file: file2};
+            }
+            return {file: null};
+        });
+
+        (isImage as jest.Mock).mockImplementation((file) => file.id === '1');
+        (isVideo as jest.Mock).mockImplementation((file) => file.id === '2');
+        (isGif as jest.Mock).mockImplementation(() => false);
+        (buildFileUrl as jest.Mock).mockImplementation((url, id) => `${url}/files/${id}`);
+        (buildFilePreviewUrl as jest.Mock).mockImplementation((url, id) => `${url}/files/${id}/preview`);
+        (getImageSize as jest.Mock).mockImplementation(() => ({width: 100, height: 100}));
+
+        const {result, waitForNextUpdate} = renderHook(() => useChannelBookmarkFiles(bookmarks, true));
+
+        await waitForNextUpdate();
+
+        expect(result.current).toHaveLength(2);
+        expect(result.current[0].id).toBe('1');
+        expect(result.current[1].id).toBe('2');
+    });
+});
diff --git a/app/hooks/gallery.test.ts b/app/hooks/gallery.test.ts
new file mode 100644
index 0000000000..a2a0c2c73a
--- /dev/null
+++ b/app/hooks/gallery.test.ts
@@ -0,0 +1,398 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+import {renderHook, act} from '@testing-library/react-hooks';
+import {useSharedValue} from 'react-native-reanimated';
+
+import {useGallery} from '@context/gallery';
+
+import {useGalleryControls, useGalleryItem, diff, useCreateAnimatedGestureHandler} from './gallery';
+
+jest.mock('react-native-reanimated', () => ({
+    Easing: {
+        bezier: jest.fn(),
+    },
+    runOnJS: jest.fn((fn) => fn),
+    useAnimatedRef: jest.fn(() => ({})),
+    useAnimatedStyle: jest.fn((fn) => fn()),
+    useEvent: jest.fn(),
+    useSharedValue: jest.fn(),
+    withTiming: jest.fn(),
+}));
+
+jest.mock('@context/gallery', () => ({
+    useGallery: jest.fn(),
+}));
+
+jest.mock('react-native', () => ({
+    Platform: {
+        OS: 'ios',
+    },
+}));
+
+describe('gallery hooks', () => {
+    test('diff', () => {
+        const context = {} as {___diffs?: any};
+        const name = 'test';
+        const value = 10;
+
+        const result = diff(context, name, value);
+
+        expect(result).toBe(0);
+        expect(context.___diffs[name].stash).toBe(0);
+        expect(context.___diffs[name].prev).toBe(value);
+    });
+
+    test('diff should return 0 for the same value', () => {
+        const context = {} as {___diffs?: any};
+        const name = 'test';
+        const value = 10;
+
+        diff(context, name, value);
+        const result = diff(context, name, value);
+
+        expect(result).toBe(0);
+        expect(context.___diffs[name].stash).toBe(0);
+        expect(context.___diffs[name].prev).toBe(value);
+    });
+
+    describe('useCreateAnimatedGestureHandler', () => {
+        const handlers = {
+            onInit: jest.fn(),
+            onGesture: jest.fn(),
+            shouldHandleEvent: jest.fn(),
+            onEvent: jest.fn(),
+            shouldCancel: jest.fn(),
+            onEnd: jest.fn(),
+            onStart: jest.fn(),
+            onActive: jest.fn(),
+            onFail: jest.fn(),
+            onCancel: jest.fn(),
+            onFinish: jest.fn(),
+            beforeEach: jest.fn(),
+            afterEach: jest.fn(),
+        };
+
+        test('iOS and state is active', () => {
+            const context = {__initialized: false, _shouldSkip: false} as any;
+
+            (useSharedValue as jest.Mock).mockImplementationOnce(() => ({value: context}));
+
+            const {result} = renderHook(() => useCreateAnimatedGestureHandler(handlers));
+            const handler = result.current;
+
+            expect(handler).toBeInstanceOf(Function);
+
+            const event = {
+                nativeEvent: {
+                    state: 4,
+                    oldState: 1,
+                    velocityX: 0,
+                    velocityY: 0,
+                },
+            };
+
+            act(() => {
+                handler(event.nativeEvent as any);
+            });
+
+            expect(handlers.onInit).toHaveBeenCalled();
+            expect(handlers.onGesture).toHaveBeenCalled();
+            expect(handlers.shouldHandleEvent).not.toHaveBeenCalled();
+            expect(handlers.onEvent).toHaveBeenCalled();
+            expect(handlers.shouldCancel).toHaveBeenCalled();
+            expect(handlers.onEnd).not.toHaveBeenCalled();
+            expect(handlers.onStart).not.toHaveBeenCalled();
+            expect(handlers.onActive).toHaveBeenCalled();
+            expect(handlers.onFail).not.toHaveBeenCalled();
+            expect(handlers.onCancel).not.toHaveBeenCalled();
+            expect(handlers.onFinish).not.toHaveBeenCalled();
+            expect(handlers.beforeEach).toHaveBeenCalled();
+            expect(handlers.afterEach).toHaveBeenCalled();
+
+            // Check the expected values of context
+            expect(context.__initialized).toBe(true);
+            expect(context._shouldSkip).toBe(false);
+        });
+
+        test('State is end, oldState is active', () => {
+            const context = {__initialized: false, _shouldSkip: false} as any;
+
+            (useSharedValue as jest.Mock).mockImplementationOnce(() => ({value: context}));
+
+            const {result} = renderHook(() => useCreateAnimatedGestureHandler(handlers));
+            const handler = result.current;
+
+            expect(handler).toBeInstanceOf(Function);
+
+            const event = {
+                nativeEvent: {
+                    state: 5,
+                    oldState: 4,
+                    velocityX: 0,
+                    velocityY: 0,
+                },
+            };
+
+            act(() => {
+                handler(event.nativeEvent as any);
+            });
+
+            expect(handlers.onEnd).toHaveBeenCalled();
+
+            // Check the expected values of context
+            expect(context.__initialized).toBe(true);
+            expect(context._shouldCancel).toBeUndefined();
+            expect(context._shouldSkip).toBeUndefined();
+        });
+
+        test('State is began, oldState is active, velocity non-zero', () => {
+            const context = {__initialized: false, _shouldSkip: false} as any;
+
+            (useSharedValue as jest.Mock).mockImplementationOnce(() => ({value: context}));
+
+            const {result} = renderHook(() => useCreateAnimatedGestureHandler(handlers));
+            const handler = result.current;
+
+            expect(handler).toBeInstanceOf(Function);
+
+            const event = {
+                nativeEvent: {
+                    state: 2,
+                    oldState: 4,
+                    velocityX: 1,
+                    velocityY: 1,
+                },
+            };
+
+            act(() => {
+                handler(event.nativeEvent as any);
+            });
+
+            expect(handlers.shouldHandleEvent).toHaveBeenCalled();
+
+            // Check the expected values of context
+            expect(context.__initialized).toBe(true);
+            expect(context._shouldCancel).toBeUndefined();
+            expect(context._shouldSkip).toBeUndefined();
+        });
+
+        test('should skip handling event if shouldHandleEvent returns false', () => {
+            const context = {__initialized: false, _shouldSkip: undefined} as any;
+
+            handlers.shouldHandleEvent.mockReturnValueOnce(false);
+            (useSharedValue as jest.Mock).mockImplementationOnce(() => ({value: context}));
+
+            const {result} = renderHook(() => useCreateAnimatedGestureHandler(handlers));
+            const handler = result.current;
+            expect(handler).toBeInstanceOf(Function);
+
+            const event = {
+                nativeEvent: {
+                    state: 2,
+                    velocityX: 1,
+                    velocityY: 1,
+                },
+            };
+
+            act(() => {
+                handler(event.nativeEvent as any);
+            });
+
+            expect(handlers.shouldHandleEvent).toHaveBeenCalled();
+            expect(context._shouldSkip).toBe(true);
+        });
+
+        test('handles shouldCancel returning true', () => {
+            const context = {__initialized: true, _shouldSkip: false} as any;
+            handlers.shouldCancel.mockReturnValueOnce(true);
+            (useSharedValue as jest.Mock).mockImplementationOnce(() => ({value: context}));
+
+            const {result} = renderHook(() => useCreateAnimatedGestureHandler(handlers));
+            const handler = result.current;
+
+            const event = {
+                nativeEvent: {
+                    state: 4, // ACTIVE
+                    oldState: 2, // BEGAN
+                    velocityX: 0,
+                    velocityY: 0,
+                },
+            };
+
+            act(() => {
+                handler(event.nativeEvent as any);
+            });
+
+            expect(handlers.shouldCancel).toHaveBeenCalled();
+            expect(handlers.onEnd).toHaveBeenCalledWith(
+                event.nativeEvent,
+                context,
+                true, // cancelled = true
+            );
+            expect(handlers.onActive).not.toHaveBeenCalled();
+        });
+
+        test('skips event handling when context._shouldSkip is undefined', () => {
+            const context = {__initialized: true} as any;
+            (useSharedValue as jest.Mock).mockImplementationOnce(() => ({value: context}));
+
+            const {result} = renderHook(() => useCreateAnimatedGestureHandler(handlers));
+            const handler = result.current;
+
+            const event = {
+                nativeEvent: {
+                    state: 4, // ACTIVE
+                    oldState: 3, // CANCELLED
+                    velocityX: 0,
+                    velocityY: 0,
+                },
+            };
+
+            act(() => {
+                handler(event.nativeEvent as any);
+            });
+
+            expect(handlers.onEvent).not.toHaveBeenCalled();
+            expect(handlers.onActive).not.toHaveBeenCalled();
+        });
+
+        test('handles CANCELLED state when oldState is ACTIVE', () => {
+            const context = {__initialized: true, _shouldSkip: false} as any;
+            (useSharedValue as jest.Mock).mockImplementationOnce(() => ({value: context}));
+
+            const {result} = renderHook(() => useCreateAnimatedGestureHandler(handlers));
+            const handler = result.current;
+
+            const event = {
+                nativeEvent: {
+                    state: 3, // CANCELLED
+                    oldState: 4, // ACTIVE
+                    velocityX: 0,
+                    velocityY: 0,
+                },
+            };
+
+            act(() => {
+                handler(event.nativeEvent as any);
+            });
+
+            expect(handlers.onCancel).toHaveBeenCalled();
+            expect(handlers.onFinish).toHaveBeenCalledWith(
+                event.nativeEvent,
+                context,
+                true, // cancelled = true
+            );
+        });
+
+        test('handles FAILED state when oldState is ACTIVE', () => {
+            const context = {__initialized: true, _shouldSkip: false} as any;
+            (useSharedValue as jest.Mock).mockImplementationOnce(() => ({value: context}));
+
+            const {result} = renderHook(() => useCreateAnimatedGestureHandler(handlers));
+            const handler = result.current;
+
+            const event = {
+                nativeEvent: {
+                    state: 1, // FAILED
+                    oldState: 4, // ACTIVE
+                    velocityX: 0,
+                    velocityY: 0,
+                },
+            };
+
+            act(() => {
+                handler(event.nativeEvent as any);
+            });
+
+            expect(handlers.onFail).toHaveBeenCalled();
+            expect(handlers.onFinish).toHaveBeenCalledWith(
+                event.nativeEvent,
+                context,
+                true, // failed = true
+            );
+        });
+    });
+
+    test('useGalleryControls', () => {
+        (useSharedValue as jest.Mock).mockImplementationOnce(() => ({value: false}));
+        const {result} = renderHook(() => useGalleryControls());
+
+        act(() => {
+            result.current.setControlsHidden(true);
+        });
+
+        expect(result.current.controlsHidden.value).toBe(true);
+
+        act(() => {
+            result.current.setControlsHidden(false);
+        });
+
+        expect(result.current.controlsHidden.value).toBe(false);
+    });
+
+    test('useGalleryControls does not update controlsHidden when same value is set', () => {
+        const mockWithTiming = jest.fn();
+        (useSharedValue as jest.Mock).mockImplementationOnce(() => ({value: true}));
+
+        const {result} = renderHook(() => useGalleryControls());
+
+        act(() => {
+            result.current.setControlsHidden(true);
+        });
+
+        expect(mockWithTiming).not.toHaveBeenCalled();
+    });
+
+    test('useGalleryItem', () => {
+        const identifier = 'test';
+        const index = 0;
+        const onPress = jest.fn();
+        const gallery = {
+            sharedValues: {
+                opacity: {value: 1},
+                activeIndex: {value: 0},
+            },
+            registerItem: jest.fn(),
+        };
+        (useGallery as jest.Mock).mockReturnValue(gallery);
+
+        const {result} = renderHook(() => useGalleryItem(identifier, index, onPress));
+
+        expect(result.current.ref).toBeDefined();
+        expect(result.current.styles).toBeDefined();
+        expect(result.current.onGestureEvent).toBeInstanceOf(Function);
+
+        act(() => {
+            result.current.onGestureEvent();
+        });
+
+        expect(gallery.sharedValues.activeIndex.value).toBe(index);
+        expect(onPress).toHaveBeenCalledWith(identifier, index);
+    });
+
+    test('useGalleryItem updates activeIndex when onGestureEvent is triggered', () => {
+        const identifier = 'test';
+        const index = 0;
+        const onPress = jest.fn();
+        const gallery = {
+            sharedValues: {
+                opacity: {value: 1},
+                activeIndex: {value: 1}, // Initial value different from index
+            },
+            registerItem: jest.fn(),
+        };
+        (useGallery as jest.Mock).mockReturnValue(gallery);
+
+        const {result} = renderHook(() => useGalleryItem(identifier, index, onPress));
+
+        expect(result.current.styles.opacity).toBe(1);
+
+        act(() => {
+            result.current.onGestureEvent();
+        });
+
+        expect(gallery.sharedValues.activeIndex.value).toBe(index);
+        expect(onPress).toHaveBeenCalledWith(identifier, index);
+    });
+});
diff --git a/app/hooks/gallery.ts b/app/hooks/gallery.ts
index 13e07db0b8..5d2ede247b 100644
--- a/app/hooks/gallery.ts
+++ b/app/hooks/gallery.ts
@@ -14,7 +14,7 @@ import {useGallery} from '@context/gallery';
 import type {Context, GestureHandlers, OnGestureEvent} from '@typings/screens/gallery';
 import type {GestureHandlerGestureEvent} from 'react-native-gesture-handler';
 
-function diff(context: any, name: string, value: any) {
+export function diff(context: any, name: string, value: any) {
     'worklet';
 
     if (!context.___diffs) {
diff --git a/app/hooks/markdown.test.ts b/app/hooks/markdown.test.ts
new file mode 100644
index 0000000000..a22569c0a8
--- /dev/null
+++ b/app/hooks/markdown.test.ts
@@ -0,0 +1,92 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+import {renderHook} from '@testing-library/react-hooks';
+
+import {getUsersByUsername} from '@utils/user';
+
+import {useMemoMentionedUser, useMemoMentionedGroup} from './markdown';
+
+import type {GroupModel, UserModel} from '@database/models/server';
+
+jest.mock('@utils/user', () => ({
+    getUsersByUsername: jest.fn(),
+}));
+
+const mockGetUsersByUsername = jest.mocked(getUsersByUsername);
+
+describe('useMemoMentionedUser', () => {
+    it('should return the mentioned user if found', () => {
+        const users = [{username: 'john_doe'} as UserModel];
+        const mentionName = 'john_doe';
+        const usersByUsername = {john_doe: users[0]};
+        mockGetUsersByUsername.mockReturnValue(usersByUsername);
+
+        const {result} = renderHook(() => useMemoMentionedUser(users, mentionName));
+
+        expect(result.current).toBe(users[0]);
+    });
+
+    it('should return undefined if the mentioned user is not found', () => {
+        const users = [{username: 'john_doe'} as UserModel];
+        const mentionName = 'jane_doe';
+        const usersByUsername = {john_doe: users[0]};
+        mockGetUsersByUsername.mockReturnValue(usersByUsername);
+
+        const {result} = renderHook(() => useMemoMentionedUser(users, mentionName));
+
+        expect(result.current).toBeUndefined();
+    });
+
+    it('should trim trailing punctuation from the mention name', () => {
+        const users = [{username: 'john_doe'} as UserModel];
+        const mentionName = 'john_doe.';
+        const usersByUsername = {john_doe: users[0]};
+        mockGetUsersByUsername.mockReturnValue(usersByUsername);
+
+        const {result} = renderHook(() => useMemoMentionedUser(users, mentionName));
+
+        expect(result.current).toBe(users[0]);
+    });
+});
+
+describe('useMemoMentionedGroup', () => {
+    it('should return the mentioned group if found', () => {
+        const groups = [{name: 'developers'} as GroupModel];
+        const user = undefined;
+        const mentionName = 'developers';
+
+        const {result} = renderHook(() => useMemoMentionedGroup(groups, user, mentionName));
+
+        expect(result.current).toBe(groups[0]);
+    });
+
+    it('should return undefined if the mentioned group is not found', () => {
+        const groups = [{name: 'developers'} as GroupModel];
+        const user = undefined;
+        const mentionName = 'designers';
+
+        const {result} = renderHook(() => useMemoMentionedGroup(groups, user, mentionName));
+
+        expect(result.current).toBeUndefined();
+    });
+
+    it('should return undefined if the user is defined', () => {
+        const groups = [{name: 'developers'} as GroupModel];
+        const user = {username: 'john_doe'} as UserModel;
+        const mentionName = 'developers';
+
+        const {result} = renderHook(() => useMemoMentionedGroup(groups, user, mentionName));
+
+        expect(result.current).toBeUndefined();
+    });
+
+    it('should trim trailing punctuation from the mention name', () => {
+        const groups = [{name: 'developers'} as GroupModel];
+        const user = undefined;
+        const mentionName = 'developers.';
+
+        const {result} = renderHook(() => useMemoMentionedGroup(groups, user, mentionName));
+
+        expect(result.current).toBe(groups[0]);
+    });
+});