snapshot of https://github.com/mattermost/mattermost.git (master, 2026-09-16; blobs > 131072B omitted)

e2e-tests/cypress/tests/integration/channels/mark_as_unread/archive_channel_mark_as_unread_spec.js

@@ -0,0 +1,75 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+// ***************************************************************
+// - [#] indicates a test step (e.g. # Go to a page)
+// - [*] indicates an assertion (e.g. * Check the title)
+// - Use element ID when selecting an element. Create one if none.
+// ***************************************************************
+
+// Stage: @prod
+// Group: @channels @mark_as_unread
+
+import {markAsUnreadShouldBeAbsent} from './helpers';
+
+describe('Channels', () => {
+    let testUser;
+    let testChannel;
+    let testTeam;
+    let post1;
+
+    before(() => {
+        cy.apiInitSetup().then(({team, user}) => {
+            testUser = user;
+            testTeam = team;
+
+            // # Create a test channel
+            cy.apiCreateChannel(team.id, 'channel-test', 'Channel').then(({channel}) => {
+                testChannel = channel;
+
+                // # Create second user and add him to the team
+                cy.apiCreateUser().then(({user: user2}) => {
+                    const otherUser = user2;
+
+                    cy.apiAddUserToTeam(team.id, otherUser.id).then(() => {
+                        cy.apiAddUserToChannel(testChannel.id, otherUser.id);
+
+                        // Another user creates posts in the channel since you can't mark your own posts unread currently
+                        cy.postMessageAs({sender: otherUser, message: 'post1', channelId: testChannel.id}).then((p1) => {
+                            post1 = p1;
+                        });
+                    });
+                });
+            });
+        });
+    });
+    it('MM-T263 Mark as Unread post menu option should not be available for archived channels', () => {
+        // # Login as testUser
+        cy.apiLogin(testUser);
+
+        // # Visit the channel
+        cy.visit(`/${testTeam.name}/channels/${testChannel.name}`);
+
+        // # Click channel header to open channel menu
+        cy.get('#channelHeaderTitle').should('contain', testChannel.display_name).click();
+
+        // * Verify that the menu is opened
+        cy.get('#channelHeaderDropdownMenu').should('be.visible').within(() => {
+            // # Archive the channel
+            cy.findByText('Archive Channel').should('be.visible').click();
+        });
+
+        // * Verify that the delete/archive channel modal is opened
+        cy.get('#deleteChannelModal').should('be.visible').within(() => {
+            // # Confirm archive
+            cy.findByText('Archive').should('be.visible').click();
+        });
+
+        // * Verify the "Mark as Unread" option is absent in post menu
+        markAsUnreadShouldBeAbsent(post1.id);
+
+        // * Verify the post is not marked as unread
+        cy.get('.NotificationSeparator').should('not.exist');
+    });
+});
+

e2e-tests/cypress/tests/integration/channels/mark_as_unread/bot_post_mark_as_unread_spec.js

@@ -0,0 +1,61 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+// ***************************************************************
+// - [#] indicates a test step (e.g. # Go to a page)
+// - [*] indicates an assertion (e.g. * Check the title)
+// - Use element ID when selecting an element. Create one if none.
+// ***************************************************************
+
+// Group: @channels @mark_as_unread
+
+import {markAsUnreadFromPost, verifyPostNextToNewMessageSeparator} from './helpers';
+
+import {beUnread} from '@/support/assertions';
+
+describe('Bot post unread message', () => {
+    let newChannel;
+    let botPost;
+    let testTeam;
+
+    before(() => {
+        // # Create and visit new channel
+        cy.apiInitSetup({
+            promoteNewUserAsAdmin: true,
+            loginAfter: true,
+        }).then(({team, channel}) => {
+            testTeam = team;
+            newChannel = channel;
+            cy.visit(`/${testTeam.name}/channels/${channel.name}`);
+        });
+
+        // # Create a bot and get userID
+        cy.apiCreateBot().then(({bot}) => {
+            const botUserId = bot.user_id;
+            cy.apiPatchUserRoles(botUserId, ['system_user system_post_all system_admin']);
+
+            // # Get token from bots id
+            cy.apiAccessToken(botUserId, 'Create token').then(({token}) => {
+                //# Add bot to team
+                cy.apiAddUserToTeam(newChannel.team_id, botUserId);
+
+                // # Post message as bot to the new channel
+                cy.postBotMessage({token, channelId: newChannel.id, message: 'this is bot message'}).then((res) => {
+                    botPost = res.data;
+                });
+            });
+        });
+    });
+
+    it('MM-T252 bot post unread', () => {
+        // # Mark the bot post as unread
+        markAsUnreadFromPost(botPost);
+
+        // * Verify the channel is unread in LHS
+        cy.visit(`/${testTeam.name}/channels/town-square`);
+        cy.get(`#sidebarItem_${newChannel.name}`).should(beUnread).click();
+
+        // * Verify the notification separator line exists and present before the unread message
+        verifyPostNextToNewMessageSeparator('this is bot message');
+    });
+});

e2e-tests/cypress/tests/integration/channels/mark_as_unread/channel_unread_spec.js

@@ -0,0 +1,132 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+// ***************************************************************
+// - [#] indicates a test step (e.g. # Go to a page)
+// - [*] indicates an assertion (e.g. * Check the title)
+// - Use element ID when selecting an element. Create one if none.
+// ***************************************************************
+
+// Group: @channels @channel
+
+import {verifyPostNextToNewMessageSeparator, switchToChannel} from './helpers';
+
+import {beRead, beUnread} from '@/support/assertions';
+
+describe('channel unread posts', () => {
+    let testUser;
+    let otherUser;
+
+    let channelA;
+    let channelB;
+
+    beforeEach(() => {
+        cy.apiAdminLogin();
+
+        // # Create testUser added to channel
+        cy.apiInitSetup().then(({team, channel, user}) => {
+            testUser = user;
+            channelA = channel;
+
+            // # Create second channel and add testUser
+            cy.apiCreateChannel(team.id, 'channel-b', 'Channel B').then((out) => {
+                channelB = out.channel;
+                cy.apiAddUserToChannel(channelB.id, testUser.id);
+            });
+
+            // # Create otherUser, add to team, and add to both channelA and channelB
+            cy.apiCreateUser().then(({user: user2}) => {
+                otherUser = user2;
+
+                cy.apiAddUserToTeam(team.id, otherUser.id).then(() => {
+                    cy.apiAddUserToChannel(channelA.id, otherUser.id);
+                    cy.apiAddUserToChannel(channelB.id, otherUser.id);
+                });
+
+                for (let index = 0; index < 5; index++) {
+                    // # Post Message as Current user
+                    const message = `hello from current user: ${index}`;
+
+                    cy.postMessageAs({sender: testUser, message, channelId: channelA.id});
+                }
+            });
+
+            cy.apiLogin(testUser);
+            cy.visit(`/${team.name}/channels/town-square`);
+        });
+    });
+
+    it('MM-T256 Mark unread before a page of message in Channel', () => {
+        // # Login as other user
+        cy.apiLogin(otherUser);
+
+        // # Switch to channelA
+        switchToChannel(channelA);
+
+        for (let index = 5; index < 40; index++) {
+            // # Post Message as Current user
+            const message = `hello from current user: ${index}`;
+
+            cy.postMessageAs({sender: testUser, message, channelId: channelA.id});
+        }
+
+        // # Mark the post which is one page above from bottom as unread
+        cy.getNthPostId(6).then((postId) => {
+            cy.get(`#post_${postId}`).scrollIntoView().should('be.visible');
+            cy.uiClickPostDropdownMenu(postId, 'Mark as Unread');
+        });
+
+        // * Verify the notification separator line exists and present before the unread message
+        verifyPostNextToNewMessageSeparator('hello from current user: 5');
+
+        // # Switch to channelB
+        switchToChannel(channelB);
+
+        // # Switch to channelA
+        switchToChannel(channelA);
+
+        // * Verify the notification separator line exists and present before the unread message
+        verifyPostNextToNewMessageSeparator('hello from current user: 5');
+    });
+
+    it('MM-T259 Mark as Unread channel remains unread when receiving new message', () => {
+        // # Login as other user
+        cy.apiLogin(otherUser);
+
+        // # Switch to channelA
+        switchToChannel(channelA);
+
+        // # Mark the last post as unread
+        cy.getLastPostId().then((postId) => {
+            cy.uiClickPostDropdownMenu(postId, 'Mark as Unread');
+        });
+
+        // * Verify the notification separator line exists and present before the unread message
+        verifyPostNextToNewMessageSeparator('hello from current user: 4');
+
+        // * Verify the channelA has unread in LHS
+        cy.get(`#sidebarItem_${channelA.name}`).should(beUnread);
+
+        for (let index = 5; index < 10; index++) {
+            // # Post Message as Current user
+            const message = `hello from current user: ${index}`;
+
+            cy.postMessageAs({sender: testUser, message, channelId: channelA.id});
+
+            // * Verify the channelA has unread in LHS even when the messages are coming through
+            cy.get(`#sidebarItem_${channelA.name}`).should(beUnread);
+        }
+
+        // # Switch to channelB
+        switchToChannel(channelB);
+
+        // * Verify the channelA has unread in LHS
+        cy.get(`#sidebarItem_${channelA.name}`).should(beUnread);
+
+        // # Switch to channelA
+        switchToChannel(channelA);
+
+        // * Verify the channelA has does not have unread in LHS
+        cy.get(`#sidebarItem_${channelA.name}`).should(beRead);
+    });
+});

e2e-tests/cypress/tests/integration/channels/mark_as_unread/helpers.js

@@ -0,0 +1,66 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+import * as TIMEOUTS from '@/fixtures/timeouts';
+
+export function markAsUnreadFromPost(post, rhs = false) {
+    const prefix = rhs ? 'rhsPost' : 'post';
+
+    cy.get(`#${prefix}_${post.id}`).scrollIntoView().should('be.visible');
+
+    cy.get('body').type('{alt}', {release: false});
+    cy.get(`#${prefix}_${post.id}`).click({force: true});
+    cy.get('body').type('{alt}', {release: true});
+}
+
+export function markAsUnreadShouldBeAbsent(postId, prefix = 'post', location = 'CENTER') {
+    cy.get(`#${prefix}_${postId}`).trigger('mouseover');
+    cy.clickPostDotMenu(postId, location);
+    cy.get(`#CENTER_dropdown_${postId}`).
+        should('be.visible').
+        within(() => {
+            cy.findByText('Mark as Unread').should('not.exist');
+        });
+    cy.get('body').type('esc');
+}
+
+export function switchToChannel(channel) {
+    cy.get(`#sidebarItem_${channel.name}`).click();
+
+    cy.get('#channelHeaderTitle', {timeout: TIMEOUTS.ONE_MIN}).should('contain', channel.display_name);
+
+    // # Wait some time for the channel to set state
+    cy.wait(TIMEOUTS.HALF_SEC);
+}
+
+export function verifyPostNextToNewMessageSeparator(message) {
+    cy.get('.NotificationSeparator').
+        should('exist').
+        parent().
+        parent().
+        parent().
+        next().
+        should('contain', message);
+}
+
+export function verifyTopSpaceForNewMessage(message) {
+    cy.get('.post-row__padding.top').
+        should('be.visible').
+        should('contain', message);
+}
+
+export function verifyBottomSpaceForNewMessage(message) {
+    cy.get('.post-row__padding.bottom').
+        should('be.visible').
+        should('contain', message);
+}
+
+export function showCursor(items) {
+    cy.expect(items).to.have.length(1);
+    expect(items[0].className).to.match(/cursor--pointer/);
+}
+
+export function notShowCursor(items) {
+    cy.expect(items).to.have.length(1);
+    expect(items[0].className).to.not.match(/cursor--pointer/);
+}

e2e-tests/cypress/tests/integration/channels/mark_as_unread/leave_channel_unread_spec.js

@@ -0,0 +1,81 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+// ***************************************************************
+// - [#] indicates a test step (e.g. # Go to a page)
+// - [*] indicates an assertion (e.g. * Check the title)
+// - Use element ID when selecting an element. Create one if none.
+// ***************************************************************
+
+// Stage: @prod
+// Group: @channels @mark_as_unread
+
+import {markAsUnreadFromPost, switchToChannel} from './helpers';
+
+import {beRead, beUnread} from '@/support/assertions';
+
+describe('Leaving channel', () => {
+    let testUser;
+    let otherUser;
+
+    let channelA;
+    let channelB;
+
+    let post1;
+
+    beforeEach(() => {
+        cy.visit('/');
+        cy.apiAdminLogin();
+        cy.apiInitSetup().then(({team, channel, user}) => {
+            testUser = user;
+            channelA = channel;
+
+            cy.apiCreateChannel(team.id, 'channel-b', 'Channel B').then((out) => {
+                channelB = out.channel;
+                cy.apiAddUserToChannel(channelB.id, testUser.id);
+            });
+
+            cy.apiCreateUser().then(({user: user2}) => {
+                otherUser = user2;
+
+                cy.apiAddUserToTeam(team.id, otherUser.id).then(() => {
+                    cy.apiAddUserToChannel(channelA.id, otherUser.id);
+
+                    cy.postMessageAs({
+                        sender: otherUser,
+                        message: 'post1',
+                        channelId: channelA.id,
+                    }).then((p1) => {
+                        post1 = p1;
+                    });
+                });
+            });
+
+            cy.apiLogin(testUser);
+            cy.visit(`/${team.name}/channels/town-square`);
+        });
+    });
+
+    it('MM-T2924_1 Channel is marked as read as soon as user leaves', () => {
+        switchToChannel(channelA);
+
+        cy.postMessageAs({sender: otherUser, message: 'post2', channelId: channelA.id});
+
+        switchToChannel(channelB);
+
+        // * Verify that channelA does not have unread in LHS
+        cy.get(`#sidebarItem_${channelA.name}`).should(beRead);
+    });
+
+    it('MM-T2924_2 Channel is left unread if post is manually marked as unread and user leaves', () => {
+        switchToChannel(channelA);
+
+        markAsUnreadFromPost(post1);
+
+        switchToChannel(channelB);
+
+        // * Verify that channelA has unread in LHS
+        cy.get(`#sidebarItem_${channelA.name}`).should(beUnread);
+    });
+});
+

e2e-tests/cypress/tests/integration/channels/mark_as_unread/mark_as_unread_spec.js

@@ -0,0 +1,422 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+// ***************************************************************
+// - [#] indicates a test step (e.g. # Go to a page)
+// - [*] indicates an assertion (e.g. * Check the title)
+// - Use element ID when selecting an element. Create one if none.
+// ***************************************************************
+
+// Group: @channels @mark_as_unread
+
+import {verifyPostNextToNewMessageSeparator, verifyTopSpaceForNewMessage, verifyBottomSpaceForNewMessage, switchToChannel, showCursor, notShowCursor} from './helpers';
+
+import {beRead, beUnread} from '@/support/assertions';
+
+describe('Mark as Unread', () => {
+    let testUser;
+    let team1;
+    let channelA;
+    let channelB;
+
+    let post1;
+    let post2;
+    let post3;
+
+    beforeEach(() => {
+        cy.apiAdminLogin();
+        cy.apiInitSetup().then(({team, channel, user}) => {
+            team1 = team;
+            testUser = user;
+            channelA = channel;
+
+            cy.apiCreateChannel(team1.id, 'channel-b', 'Channel B').then((out) => {
+                channelB = out.channel;
+                cy.apiAddUserToChannel(channelB.id, testUser.id);
+            });
+
+            cy.apiCreateUser().then(({user: user2}) => {
+                const otherUser = user2;
+
+                cy.apiAddUserToTeam(team1.id, otherUser.id).then(() => {
+                    cy.apiAddUserToChannel(channelA.id, otherUser.id);
+
+                    // Another user creates posts in the channel since you can't mark your own posts unread currently
+                    cy.postMessageAs({
+                        sender: otherUser,
+                        message: 'post1',
+                        channelId: channelA.id,
+                    }).then((p1) => {
+                        post1 = p1;
+
+                        cy.postMessageAs({
+                            sender: otherUser,
+                            message: 'post2',
+                            channelId: channelA.id,
+                        }).then((p2) => {
+                            post2 = p2;
+
+                            cy.postMessageAs({
+                                sender: otherUser,
+                                message: 'post3',
+                                channelId: channelA.id,
+                                rootId: post1.id,
+                            }).then((post) => {
+                                post3 = post;
+                            });
+                        });
+                    });
+                });
+            });
+
+            cy.apiLogin(testUser);
+            cy.visit(`/${team1.name}/channels/town-square`);
+        });
+    });
+
+    it('Channel should appear unread after switching away from channel and be read after switching back', () => {
+        // Starts unread
+        cy.get(`#sidebarItem_${channelA.name}`).should(beUnread);
+
+        switchToChannel(channelA);
+
+        // Then becomes read when you view the channel
+        cy.get(`#sidebarItem_${channelA.name}`).should(beRead);
+
+        markAsUnreadFromPost(post2);
+
+        // Then becomes unread when the channel is marked as unread
+        cy.get(`#sidebarItem_${channelA.name}`).should(beUnread);
+
+        switchToChannel(channelB);
+
+        // Then stays unread when switching away
+        cy.get(`#sidebarItem_${channelA.name}`).should(beUnread);
+
+        switchToChannel(channelA);
+
+        // And becomes read when switching back
+        cy.get(`#sidebarItem_${channelA.name}`).should(beRead);
+    });
+
+    it('MM-T5223 The latest post should appear unread after marking the channel as unread', () => {
+        // channelA starts unread, then becomes read after you viewed
+        // and switched to channelB
+        cy.get(`#sidebarItem_${channelA.name}`).should(beUnread);
+        switchToChannel(channelA);
+        cy.get(`#sidebarItem_${channelA.name}`).should(beRead);
+        switchToChannel(channelB);
+
+        // After mark channelA with the LHS mark as unread option, channelA
+        // should appear unread
+        cy.get(`#sidebarItem_${channelA.name}`).find('.SidebarMenu').click({force: true});
+        cy.get(`#markAsUnread-${channelA.id}`).click();
+        cy.get(`#sidebarItem_${channelA.name}`).should(beUnread);
+
+        // After switching back to channelA,
+        // the New Messages line should appear above the last post (post3)
+        cy.get(`#sidebarItem_${channelA.name}`).click();
+        verifyPostNextToNewMessageSeparator('post3');
+    });
+
+    it('MM-T5224 The latest post should appear unread after marking the channel as unread with alt/option+left-click on channel sidebar item', () => {
+        // channelA starts unread, then becomes read after you viewed
+        // and switched to channelB
+        cy.get(`#sidebarItem_${channelA.name}`).should(beUnread);
+        switchToChannel(channelA);
+        cy.get(`#sidebarItem_${channelA.name}`).should(beRead);
+        switchToChannel(channelB);
+
+        // After mark channelA with alt/option+left-click, channelA
+        // should appear unread
+        cy.get(`#sidebarItem_${channelA.name}`).type('{alt}', {release: false}).click();
+        cy.get(`#sidebarItem_${channelA.name}`).should(beUnread);
+
+        // After switching back to channelA,
+        // the New Messages line should appear above the last post (post3)
+        cy.get(`#sidebarItem_${channelA.name}`).click();
+        verifyPostNextToNewMessageSeparator('post3');
+    });
+
+    it('MM-T257 Mark as Unread when bringing window into focus', () => {
+        // * Verify channels are unread
+        cy.get(`#sidebarItem_${channelA.name}`).should(beUnread);
+        cy.get(`#sidebarItem_${channelB.name}`).should(beUnread);
+
+        // # Navigate to integration screen (away from chat/main screen)
+        cy.visit(`/${team1.name}/integrations/`);
+
+        // # Navigate back to chat/main screen
+        cy.visit(`/${team1.name}/channels/town-square`);
+
+        // * Verify channels are unread
+        cy.get(`#sidebarItem_${channelA.name}`).should(beUnread);
+        cy.get(`#sidebarItem_${channelB.name}`).should(beUnread);
+
+        switchToChannel(channelA);
+        switchToChannel(channelB);
+
+        // * Verify channel are read
+        cy.get(`#sidebarItem_${channelA.name}`).should(beRead);
+        cy.get(`#sidebarItem_${channelB.name}`).should(beRead);
+    });
+
+    it('New messages line should remain after switching back to channel', () => {
+        switchToChannel(channelA);
+
+        // Starts not visible
+        cy.get('.NotificationSeparator').should('not.exist');
+
+        markAsUnreadFromPost(post2);
+
+        // Then becomes visible
+        cy.get('.NotificationSeparator').should('exist');
+
+        switchToChannel(channelB);
+        switchToChannel(channelA);
+
+        // Then stays visible when switching back to channel
+        cy.get('.NotificationSeparator').should('exist');
+
+        switchToChannel(channelB);
+        switchToChannel(channelA);
+
+        // Then finally disappears when switching back a second time
+        cy.get('.NotificationSeparator').should('not.exist');
+    });
+
+    it('MM-T260 Mark as Unread New Messages line extra space moves with it', () => {
+        switchToChannel(channelA);
+
+        markAsUnreadFromPost(post2);
+
+        // The New Messages line should appear above the selected post
+        verifyPostNextToNewMessageSeparator('post2');
+
+        // Top separator space should appear above the selected post
+        verifyTopSpaceForNewMessage('post2');
+
+        // Bottom separator space should appear below the post
+        verifyBottomSpaceForNewMessage('post1');
+
+        markAsUnreadFromPost(post1);
+
+        // The New Messages line should appear above the selected post
+        verifyPostNextToNewMessageSeparator('post1');
+
+        // Top separator space should appear above the selected post
+        verifyTopSpaceForNewMessage('post1');
+
+        // Bottom separator space should appear below the post by user
+        verifyBottomSpaceForNewMessage('System');
+
+        markAsUnreadFromPost(post3);
+
+        // The New Messages line should appear above the selected post
+        verifyPostNextToNewMessageSeparator('post3');
+
+        // Top separator space should appear above the selected post
+        verifyTopSpaceForNewMessage('post3');
+
+        // Bottom separator space should appear below the post
+        verifyBottomSpaceForNewMessage('post2');
+    });
+
+    it('Should be able to mark channel as unread by alt-clicking on RHS', () => {
+        switchToChannel(channelA);
+
+        // Show the RHS
+        cy.get(`#CENTER_commentIcon_${post3.id}`).click({force: true});
+
+        markAsUnreadFromPost(post1, true);
+
+        // The New Messages line should appear above the selected post
+        verifyPostNextToNewMessageSeparator('post1');
+
+        markAsUnreadFromPost(post3, true);
+
+        // The New Messages line should appear above the selected post
+        verifyPostNextToNewMessageSeparator('post3');
+    });
+
+    it('Should show cursor pointer when holding down alt', () => {
+        const componentIds = [
+            `#post_${post1.id}`,
+            `#post_${post2.id}`,
+            `#post_${post3.id}`,
+            `#rhsPost_${post1.id}`,
+            `#rhsPost_${post3.id}`,
+        ];
+
+        switchToChannel(channelA);
+
+        // Show the RHS
+        cy.get(`#CENTER_commentIcon_${post3.id}`).click({force: true});
+
+        // Pretend that we start hovering over each and then hold alt afterwards
+        for (const componentId of componentIds) {
+            // * Verify that we don't show the pointer on mouseover
+            cy.get(componentId).trigger('mouseover').should(notShowCursor);
+
+            // * Verify that we show the pointer after pressing alt
+            cy.get(componentId).trigger('keydown', {altKey: true}).should(showCursor);
+
+            // * Verify that we stop showing the pointer after releasing alt
+            cy.get(componentId).trigger('keydown', {altKey: false}).should(notShowCursor);
+
+            // # Move the mouse away from the post
+            cy.get(componentId).trigger('mouseout');
+        }
+
+        // Pretend that we hold down alt and then hover over each post
+        for (const componentId of componentIds) {
+            // * Verify that we don't show the pointer on mouseover
+            cy.get(componentId).trigger('mouseover', {altKey: true}).should(showCursor);
+
+            // # Move the mouse away from the post
+            cy.get(componentId).trigger('mouseout', {altKey: true}).should(notShowCursor);
+        }
+    });
+
+    it('Marking a channel as unread from another session while viewing channel', () => {
+        switchToChannel(channelA);
+
+        cy.get(`#sidebarItem_${channelA.name}`).should(beRead);
+
+        markAsUnreadFromAnotherSession(post2, testUser);
+
+        // The channel should now be unread
+        cy.get(`#sidebarItem_${channelA.name}`).should(beUnread);
+
+        // The New Messages line should appear above the selected post
+        verifyPostNextToNewMessageSeparator('post2');
+
+        switchToChannel(channelB);
+
+        // Then stays unread when switching away
+        cy.get(`#sidebarItem_${channelA.name}`).should(beUnread);
+
+        switchToChannel(channelA);
+
+        // And becomes read when switching back
+        cy.get(`#sidebarItem_${channelA.name}`).should(beRead);
+
+        // The New Messages line should appear above the selected post
+        verifyPostNextToNewMessageSeparator('post2');
+    });
+
+    it('Marking a channel as unread from another session while viewing another channel', () => {
+        switchToChannel(channelA);
+        switchToChannel(channelB);
+
+        cy.get(`#sidebarItem_${channelA.name}`).should(beRead);
+
+        markAsUnreadFromAnotherSession(post2, testUser);
+
+        // The channel should now be unread
+        cy.get(`#sidebarItem_${channelA.name}`).should(beUnread);
+
+        switchToChannel(channelA);
+
+        // And becomes read when switching back
+        cy.get(`#sidebarItem_${channelA.name}`).should(beRead);
+
+        // The New Messages line should appear above the selected post
+        verifyPostNextToNewMessageSeparator('post2');
+    });
+
+    it('MM-T244 Webapp: Post menu item `Mark as Unread` appearance', () => {
+        switchToChannel(channelA);
+        cy.get(`#sidebarItem_${channelA.name}`).should(beRead);
+        postMessage(post1.message);
+        cy.getLastPostId().then((postId) => {
+            cy.clickPostDotMenu(postId);
+            cy.get('ul.Menu__content.dropdown-menu').
+                as('menuOptions').
+                should('be.visible').
+                scrollIntoView();
+
+            // # Post menu item `Mark as Unread` should be visible
+            cy.get('@menuOptions').
+                find('[aria-label="Mark as Unread"]').
+                as('markAsReadElement').
+                should('be.visible');
+
+            // # Shrink the window and verify post menu options in the mobile view
+            cy.viewport('iphone-5');
+            cy.get('@markAsReadElement').should('be.visible');
+
+            // * Verify there are no extra divider lines at the bottom of the menu for the non-admin user
+            cy.findByText('Edit').should('not.exist');
+            cy.findByText('Delete').should('not.exist');
+
+            // * Verify there are extra divider lines at the bottom
+            cy.get('ul.Menu__content').find('li.MenuItem').each(($listElement) => {
+                cy.wrap($listElement).find('button').then(($buttonElement) => {
+                    cy.wrap($buttonElement).invoke('attr', 'aria-label').then((ariaLabel) => {
+                        if (ariaLabel !== 'Copy Text') {
+                            cy.wrap($buttonElement).should('have.css', 'border-color', 'rgba(63, 67, 80, 0.12)');
+                        }
+                    });
+                });
+            });
+        });
+    });
+
+    it('Should be able to mark channel as unread from post menu', () => {
+        switchToChannel(channelA);
+
+        // # Mark post2 as unread
+        cy.uiClickPostDropdownMenu(post2.id, 'Mark as Unread');
+
+        // The New Messages line should appear above the selected post
+        verifyPostNextToNewMessageSeparator('post2');
+
+        // # Mark post1 as unread
+        cy.uiClickPostDropdownMenu(post1.id, 'Mark as Unread');
+
+        // The New Messages line should appear above the selected post
+        verifyPostNextToNewMessageSeparator('post1');
+
+        // # Mark post3 as unread
+        cy.uiClickPostDropdownMenu(post3.id, 'Mark as Unread');
+
+        // The New Messages line should appear above the selected post
+        verifyPostNextToNewMessageSeparator('post3');
+    });
+
+    it('Should be able to mark channel as unread from RHS post menu', () => {
+        switchToChannel(channelA);
+
+        // Show the RHS
+        cy.get(`#CENTER_commentIcon_${post3.id}`).click({force: true});
+
+        // # Mark post1 as unread in RHS as root thread
+        cy.uiClickPostDropdownMenu(post1.id, 'Mark as Unread', 'RHS_ROOT');
+
+        // The New Messages line should appear above the selected post
+        verifyPostNextToNewMessageSeparator('post1');
+
+        // # Mark post3 as unread in RHS as comment
+        cy.uiClickPostDropdownMenu(post3.id, 'Mark as Unread', 'RHS_COMMENT');
+
+        // The New Messages line should appear above the selected post
+        verifyPostNextToNewMessageSeparator('post3');
+    });
+});
+
+function markAsUnreadFromPost(post, rhs = false) {
+    const prefix = rhs ? 'rhsPost' : 'post';
+
+    cy.get('body').type('{alt}', {release: false});
+    cy.get(`#${prefix}_${post.id}`).click({force: true});
+    cy.get('body').type('{alt}', {release: true});
+}
+
+function markAsUnreadFromAnotherSession(post, user) {
+    cy.externalRequest({
+        user,
+        method: 'post',
+        path: `users/${user.id}/posts/${post.id}/set_unread`,
+    });
+}

e2e-tests/cypress/tests/integration/channels/mark_as_unread/mark_as_unread_using_shortcuts_spec.js

@@ -0,0 +1,94 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+// ***************************************************************
+// - [#] indicates a test step (e.g. # Go to a page)
+// - [*] indicates an assertion (e.g. * Check the title)
+// - Use element ID when selecting an element. Create one if none.
+// ***************************************************************
+
+// Stage: @prod
+// Group: @channels @mark_as_unread
+
+import {verifyPostNextToNewMessageSeparator, switchToChannel, showCursor} from './helpers';
+
+import {beRead, beUnread} from '@/support/assertions';
+
+describe('Mark as Unread', () => {
+    let testUser;
+
+    let channelA;
+    let channelB;
+
+    let post1;
+    let post2;
+
+    before(() => {
+        cy.apiInitSetup().then(({team, channel, user}) => {
+            testUser = user;
+            channelA = channel;
+
+            // # Create second channel and add testUser
+            cy.apiCreateChannel(team.id, 'channel-b', 'Channel B').then((out) => {
+                channelB = out.channel;
+                cy.apiAddUserToChannel(channelB.id, testUser.id);
+            });
+
+            // # Create second user and add him to the team
+            cy.apiCreateUser().then(({user: user2}) => {
+                const otherUser = user2;
+
+                cy.apiAddUserToTeam(team.id, otherUser.id).then(() => {
+                    cy.apiAddUserToChannel(channelA.id, otherUser.id);
+
+                    // Another user creates posts in the channel since you can't mark your own posts unread currently
+                    cy.postMessageAs({sender: otherUser, message: 'post1', channelId: channelA.id}).then((p1) => {
+                        post1 = p1;
+
+                        cy.postMessageAs({sender: otherUser, message: 'post2', channelId: channelA.id}).then((p2) => {
+                            post2 = p2;
+                        });
+                    });
+                });
+            });
+
+            cy.apiLogin(testUser);
+            cy.visit(`/${team.name}/channels/${channelA.name}`);
+        });
+    });
+
+    it('MM-T251 using shortcuts to make post unread', () => {
+        // * Hover on the post with holding alt should show cursor
+        cy.get(`#post_${post2.id}`).trigger('mouseover').type('{alt}', {release: false}).should(showCursor);
+
+        // # Mouse click on the post
+        cy.get(`#post_${post2.id}`).click();
+
+        // * Verify the post is marked as unread
+        verifyPostNextToNewMessageSeparator('post2');
+
+        // * Verify the channelA has unread in LHS
+        cy.get(`#sidebarItem_${channelA.name}`).should(beUnread);
+
+        // # Switch to channelB
+        switchToChannel(channelB);
+
+        // # Switch to channelA
+        switchToChannel(channelA);
+
+        // * Verify the channelB does not have unread in LHS
+        cy.get(`#sidebarItem_${channelB.name}`).should(beRead);
+
+        // # Open RHS (reply thread)
+        cy.clickPostCommentIcon(post1.id);
+
+        // # Mark the post as unread from RHS
+        cy.uiClickPostDropdownMenu(post1.id, 'Mark as Unread', 'RHS_ROOT');
+
+        // * Verify the New Messages line should appear above the selected post
+        verifyPostNextToNewMessageSeparator('post1');
+
+        // * Verify the channelA has unread in LHS
+        cy.get(`#sidebarItem_${channelA.name}`).should(beUnread);
+    });
+});

e2e-tests/cypress/tests/integration/channels/mark_as_unread/mark_gm_as_unread_spec.js

@@ -0,0 +1,92 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+// ***************************************************************
+// - [#] indicates a test step (e.g. # Go to a page)
+// - [*] indicates an assertion (e.g. * Check the title)
+// - Use element ID when selecting an element. Create one if none.
+// ***************************************************************
+
+// Stage: @prod
+// Group: @channels @mark_as_unread
+
+import {verifyPostNextToNewMessageSeparator} from './helpers';
+
+import * as TIMEOUTS from '@/fixtures/timeouts';
+
+describe('Mark as Unread', () => {
+    let testUser;
+    let otherUser1;
+    let otherUser2;
+
+    before(() => {
+        // # Create testUser added to channel
+        cy.apiInitSetup().then(({team, user}) => {
+            testUser = user;
+
+            // # Create second user and add to the team
+            cy.apiCreateUser({prefix: 'otherA'}).then(({user: newUser}) => {
+                otherUser1 = newUser;
+
+                cy.apiAddUserToTeam(team.id, newUser.id);
+            });
+
+            // # Create third user and add to the team
+            cy.apiCreateUser({prefix: 'otherB'}).then(({user: newUser}) => {
+                otherUser2 = newUser;
+
+                cy.apiAddUserToTeam(team.id, newUser.id);
+            });
+
+            // # Login as test user and go to town square
+            cy.apiLogin(testUser);
+            cy.visit(`/${team.name}/channels/town-square`);
+        });
+    });
+
+    it('MM-T249 Mark GM post as unread', () => {
+        const userGroupIds = [testUser.id, otherUser1.id, otherUser2.id];
+
+        // # Create a group channel for 3 users
+        cy.apiCreateGroupChannel(userGroupIds).then(({channel: gmChannel}) => {
+            // # Visit the channel using the name using the channels route
+            for (let index = 0; index < 8; index++) {
+                // # Post Message as otherUser1
+                cy.postMessageAs({sender: otherUser1, message: `this is from user: ${otherUser1.id}, ${index}`, channelId: gmChannel.id});
+
+                // # Post Message as otherUser2
+                cy.postMessageAs({sender: otherUser2, message: `this is from user: ${otherUser2.id}, ${index}`, channelId: gmChannel.id});
+            }
+
+            // # Go to the group message channel
+            cy.get(`#sidebarItem_${gmChannel.name}`).click();
+            cy.reload();
+
+            // # Mark the post to be unread
+            cy.getNthPostId(-2).then((postId) => {
+                cy.uiClickPostDropdownMenu(postId, 'Mark as Unread');
+            });
+
+            // * Verify the notification separator line exists and present before the unread message
+            verifyPostNextToNewMessageSeparator(`this is from user: ${otherUser1.id}, 7`);
+
+            // * Verify the group message in LHS is unread
+            cy.get(`#sidebarItem_${gmChannel.name}`).should('have.attr', 'aria-label', `${otherUser1.username}, ${otherUser2.username} 2 mentions`);
+
+            // # Leave the group message channel
+            cy.get('#sidebarItem_town-square').click();
+
+            // * Verify the group message in LHS is unread
+            cy.get(`#sidebarItem_${gmChannel.name}`).should('have.attr', 'aria-label', `${otherUser1.username}, ${otherUser2.username} 2 mentions`);
+
+            // # Go to the group message channel
+            cy.get(`#sidebarItem_${gmChannel.name}`).click().wait(TIMEOUTS.ONE_SEC);
+
+            // * Verify the group message in LHS is read
+            cy.get(`#sidebarItem_${gmChannel.name}`).should('exist').should('not.have.attr', 'aria-label', `${otherUser1.username}, ${otherUser2.username} 2 mentions`);
+
+            // * Verify the notification separator line exists and present before the unread message
+            verifyPostNextToNewMessageSeparator(`this is from user: ${otherUser1.id}, 7`);
+        });
+    });
+});

e2e-tests/cypress/tests/integration/channels/mark_as_unread/mark_mentions_as_unread_spec.js

@@ -0,0 +1,186 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+// ***************************************************************
+// - [#] indicates a test step (e.g. # Go to a page)
+// - [*] indicates an assertion (e.g. * Check the title)
+// - Use element ID when selecting an element. Create one if none.
+// ***************************************************************
+
+// Stage: @prod
+// Group: @channels @mark_as_unread
+
+import {verifyPostNextToNewMessageSeparator, switchToChannel} from './helpers';
+
+import {beUnread} from '@/support/assertions';
+
+describe('Mark post with mentions as unread', () => {
+    let userA;
+    let userB;
+
+    let channelA;
+    let channelB;
+
+    let testTeam;
+
+    before(() => {
+        cy.apiInitSetup().then(({team, user, channel}) => {
+            userA = user;
+            channelA = channel;
+            testTeam = team;
+
+            // # Create second channel and add userA
+            cy.apiCreateChannel(team.id, 'channel-b', 'Channel B').then((out) => {
+                channelB = out.channel;
+                cy.apiAddUserToChannel(channelB.id, userA.id);
+            });
+
+            // # Create a second user
+            cy.apiCreateUser().then(({user: user2}) => {
+                userB = user2;
+
+                // # Add userB to channel team and channels
+                cy.apiAddUserToTeam(testTeam.id, userB.id).then(() => {
+                    cy.apiAddUserToChannel(channelA.id, userB.id);
+                    cy.apiAddUserToChannel(channelB.id, userB.id);
+                });
+
+                cy.visit(`/${testTeam.name}/channels/town-square`);
+            });
+        });
+    });
+
+    it('MM-T247 Marks posts with mentions as unread', () => {
+        // # Login as userB
+        cy.apiLogin(userB);
+        cy.visit(`/${testTeam.name}/channels/town-square`);
+
+        // # Navigate to both channels, so the new messages line appears above posts
+        switchToChannel(channelA);
+        switchToChannel(channelB);
+
+        // # Mention userB in channel A as userA
+        cy.postMessageAs({
+            sender: userA,
+            message: `@${userB.username} : hello1`,
+            channelId: channelA.id,
+        });
+
+        // * Verify that channelA has unread in LHS
+        cy.get(`#sidebarItem_${channelA.name}`).should(beUnread);
+
+        // * Verify that ChannelA has unread mention in LHS
+        cy.get(`#sidebarItem_${channelA.name}`).children('#unreadMentions').should('have.text', '1');
+
+        // # Navigate to channel A
+        switchToChannel(channelA);
+
+        // * Verify that ChannelA no longer has unread mention in LHS
+        cy.get(`#sidebarItem_${channelA.name}`).children('#unreadMentions').should('not.exist');
+
+        // * Verify that new message separator exists above the unread message
+        verifyPostNextToNewMessageSeparator(`@${userB.username} : hello1`);
+
+        // # Navigate to channel B
+        switchToChannel(channelB);
+
+        // # Navigate back to channel A
+        switchToChannel(channelA);
+
+        // * Verify that new message separator is gone
+        cy.get('.NotificationSeparator').should('not.exist');
+
+        // # Mention userB in channel B as userA
+        cy.postMessageAs({
+            sender: userA,
+            message: `@${userB.username} : hello2`,
+            channelId: channelB.id,
+        });
+
+        // # Navigate to channel B
+        switchToChannel(channelB);
+
+        // * Verify that new message separator exists above the unread message
+        verifyPostNextToNewMessageSeparator(`@${userB.username} : hello2`);
+
+        // # Refresh the page
+        cy.reload();
+
+        // * Verify the new message separator is gone
+        cy.get('.NotificationSeparator').should('not.exist');
+
+        // # Mention userB in channelA as userA
+        cy.postMessageAs({
+            sender: userA,
+            message: `@${userB.username} : hello3`,
+            channelId: channelA.id,
+        });
+
+        // # Navigate back to channel A
+        switchToChannel(channelA);
+
+        // * Verify the new message separator exists above the unread message
+        verifyPostNextToNewMessageSeparator(`@${userB.username} : hello3`);
+
+        // # Get the ID of the last post
+        cy.getLastPostId().then((postId) => {
+            // # Mark last post as unread from menu
+            cy.uiClickPostDropdownMenu(postId, 'Mark as Unread');
+        });
+
+        // * Verify the new message separator still exists above the unread message
+        verifyPostNextToNewMessageSeparator(`@${userB.username} : hello3`);
+
+        // * Verify that channelA has unread in LHS
+        cy.get(`#sidebarItem_${channelA.name}`).should(beUnread);
+
+        // * Verify that ChannelA has unread mention in LHS
+        cy.get(`#sidebarItem_${channelA.name}`).children('#unreadMentions').should('have.text', '1');
+
+        // # Navigate to channel B
+        switchToChannel(channelB);
+
+        // # Navigate back to channel A
+        switchToChannel(channelA);
+
+        // * Verify the new message separator still exists above the unread message
+        verifyPostNextToNewMessageSeparator(`@${userB.username} : hello3`);
+
+        // * Verify that ChannelA no longer has unread mention in LHS
+        cy.get(`#sidebarItem_${channelA.name}`).children('#unreadMentions').should('not.exist');
+
+        // # Mention userB in channelB as userA
+        cy.postMessageAs({
+            sender: userA,
+            message: `@${userB.username} : hello4`,
+            channelId: channelB.id,
+        });
+
+        // # Navigate to channel B
+        switchToChannel(channelB);
+
+        // # Get the ID of the last post
+        cy.getLastPostId().then((postId) => {
+            // # Mark last post as unread from menu
+            cy.uiClickPostDropdownMenu(postId, 'Mark as Unread');
+        });
+
+        // * Verify the new message separator exists above the unread message
+        verifyPostNextToNewMessageSeparator(`@${userB.username} : hello4`);
+
+        // * Verify that ChannelB has unread mention in LHS
+        cy.get(`#sidebarItem_${channelB.name}`).children('#unreadMentions').should('have.text', '1');
+
+        // # Refresh the page
+        cy.reload();
+
+        // * Verify the new message separator still exists above the unread message
+        verifyPostNextToNewMessageSeparator(`@${userB.username} : hello4`);
+
+        // # Navigate to channel A
+        switchToChannel(channelA);
+
+        // * Verify that ChannelB no longer has unread mention in LHS
+        cy.get(`#sidebarItem_${channelB.name}`).children('#unreadMentions').should('not.exist');
+    });
+});

e2e-tests/cypress/tests/integration/channels/mark_as_unread/toast_appears_unread_spec.js

@@ -0,0 +1,112 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+// ***************************************************************
+// - [#] indicates a test step (e.g. # Go to a page)
+// - [*] indicates an assertion (e.g. * Check the title)
+// - Use element ID when selecting an element. Create one if none.
+// ***************************************************************
+
+// Group: @channels @mark_as_unread
+
+import {markAsUnreadFromPost, switchToChannel} from './helpers';
+
+import * as TIMEOUTS from '@/fixtures/timeouts';
+
+describe('Verify unread toast appears after repeated manual marking post as unread', () => {
+    let firstPost;
+    let secondPost;
+
+    const offTopicChannel = {name: 'off-topic', display_name: 'Off-Topic'};
+    let testChannel;
+
+    before(() => {
+        cy.apiInitSetup().then(({team, user, channel}) => {
+            testChannel = channel;
+
+            cy.apiCreateUser({prefix: 'other'}).then(({user: otherUser}) => {
+                cy.apiAddUserToTeam(team.id, otherUser.id).then(() => {
+                    cy.apiAddUserToChannel(testChannel.id, otherUser.id);
+
+                    // Toast only seems to appear after first visiting the channel
+                    // So we need to visit the channel then navigate away
+                    cy.apiLogin(user);
+                    cy.visit(`/${team.name}/channels/${testChannel.name}`);
+                    switchToChannel(offTopicChannel);
+
+                    // Ensure that the Off-Topic channel has loaded successfully, before posting messages in the other channel
+                    cy.get('#channelHeaderTitle').should('be.visible').and('contain.text', offTopicChannel.display_name);
+
+                    cy.wait(TIMEOUTS.ONE_SEC).postMessageAs({
+                        sender: otherUser,
+                        message: 'First message',
+                        channelId: testChannel.id,
+                    }).then((post) => {
+                        firstPost = post;
+
+                        cy.postMessageAs({
+                            sender: otherUser,
+                            message: 'Second message',
+                            channelId: testChannel.id,
+                        }).then((post2) => {
+                            secondPost = post2;
+
+                            // Add posts so that scroll is available
+                            Cypress._.times(30, (index) => {
+                                cy.postMessageAs({
+                                    sender: otherUser,
+                                    message: `${index.toString()}\nsecond line\nthird line\nfourth line`,
+                                    channelId: testChannel.id,
+                                });
+                            });
+                        });
+                    });
+                });
+            });
+        });
+    });
+
+    it('MM-T1429 Toast when navigating to channel with unread messages and after repeated marking as unread', () => {
+        // # Switch to town square channel that has unread messages
+        switchToChannel(testChannel);
+
+        // * Check that the toast is visible
+        cy.get('div.toast').should('be.visible');
+
+        // # Scroll to the bottom of the posts
+        cy.get('.post-list__dynamic').scrollTo('bottom');
+
+        // * Check that the toast is not visible
+        cy.get('div.toast').should('not.exist');
+
+        // # Mark the first post as unread
+        markAsUnreadFromPost(firstPost);
+
+        // * Check that the toast is now visible
+        cy.get('div.toast').should('be.visible');
+
+        // # Scroll to the bottom of the posts
+        cy.get('.post-list__dynamic').scrollTo('bottom');
+
+        // * Check that the toast is not visible
+        cy.get('div.toast').should('not.exist');
+
+        // # Mark the second post as unread
+        markAsUnreadFromPost(secondPost);
+
+        // * Check that the toast is now visible
+        cy.get('div.toast').should('be.visible');
+
+        // # Switch channels
+        switchToChannel(offTopicChannel);
+
+        // * Check that the toast is not visible
+        cy.get('div.toast').should('not.exist');
+
+        // # Switch channels back
+        switchToChannel(testChannel);
+
+        // * Check that the toast is now visible
+        cy.get('div.toast').should('be.visible');
+    });
+});

e2e-tests/cypress/tests/integration/channels/mark_as_unread/unread_toast_count_spec.js

@@ -0,0 +1,75 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+// ***************************************************************
+// - [#] indicates a test step (e.g. # Go to a page)
+// - [*] indicates an assertion (e.g. * Check the title)
+// - Use element ID when selecting an element. Create one if none.
+// ***************************************************************
+
+// Group: @channels @mark_as_unread
+
+describe('Verify unread toast appears after repeated manual marking post as unread', () => {
+    let currentChannel;
+
+    before(() => {
+        cy.apiInitSetup().then(({team, channel, user}) => {
+            currentChannel = channel;
+            cy.apiCreateUser().then(({user: user2}) => {
+                cy.apiAddUserToTeam(team.id, user2.id).then(() => {
+                    cy.apiAddUserToChannel(channel.id, user2.id);
+
+                    // # Create a page full of messages
+                    Cypress._.times(30, (i) => {
+                        cy.postMessageAs({
+                            sender: user2,
+                            message: `post${i}`,
+                            channelId: channel.id,
+                        });
+                    });
+
+                    // # Make a mentioned message
+                    cy.postMessageAs({
+                        sender: user2,
+                        message: `hi @${user.username}`,
+                        channelId: channel.id,
+                    });
+
+                    // # Login as user
+                    cy.apiLogin(user);
+
+                    // # Visit the channel
+                    cy.visit(`/${team.name}/channels/${channel.name}`);
+
+                    // # Post a reply on RHS
+                    cy.getLastPostId().then((postId) => {
+                        cy.clickPostCommentIcon(postId);
+                        cy.get('#rhsContainer').should('be.visible');
+                        const replyMessage = 'A reply to an older post';
+                        cy.postMessageReplyInRHS(replyMessage);
+                    });
+                });
+            });
+        });
+    });
+
+    it('MM-T254 Rehydrate mention badge after post is marked as Unread', () => {
+        // # Mark the first post as unread
+        cy.getNthPostId(1).then((postId) => {
+            cy.get(`#post_${postId}`).scrollIntoView().should('be.visible');
+            cy.uiClickPostDropdownMenu(postId, 'Mark as Unread');
+        });
+
+        // * Check that the toast is visible
+        cy.get('div.toast').should('be.visible').then(() => {
+            // * Check that the message is correct and all the mentions and replies are counted in toast
+            cy.get('div.toast__message>span').should('be.visible').contains('30 new messages');
+
+            cy.get(`#sidebarItem_${currentChannel.name}`).
+                scrollIntoView().
+                find('#unreadMentions').
+                should('be.visible').
+                and('have.text', '1');
+        });
+    });
+});