[FIX][REF] mail: several thread windows fixes

This commit fixes some bugs on thread windows, and make some
improvements on tests related to thread windows.

Fixes:

	1. Correctly position last visible thread window when there are more
	   open thread windows than available slots.
	2. Closing a thread window now marks it as read.
	3. Can now fold/unfold the blank thread window (aka 'New' thread window).

Tests cleaning:

	1. Removed unnecessary 'before assertions' in thread window tests.
	   > Solved with this: https://github.com/odoo/odoo/commit/9b1daa1218f7adf9d741afba607ef5b55b16e3e6
	1. Added basic rendering test for a (non-blank) thread window.
	2. Cleaned thread window tests
	   > Split in different files.
	   > Grouped in 'Thread Window' QUnit module.

3 files changed, 798 insertions, 0 deletions

diff --git a/addons/mail/static/tests/thread_window/basic_thread_window_tests.js b/addons/mail/static/tests/thread_window/basic_thread_window_tests.js
new file mode 100644
index 00000000000..ffda7d95700
--- /dev/null
+++ b/addons/mail/static/tests/thread_window/basic_thread_window_tests.js
@@ -0,0 +1,253 @@
+odoo.define('mail.basicThreadWindowTests', function (require) {
+"use strict";
+
+var mailTestUtils = require('mail.testUtils');
+
+var framework = require('web.framework');
+var testUtils = require('web.test_utils');
+var Widget = require('web.Widget');
+
+QUnit.module('mail', {}, function () {
+QUnit.module('Thread Window', {}, function () {
+QUnit.module('Basic', {
+    beforeEach: function () {
+        var self = this;
+
+        // define channel to link to chat window
+        this.data = {
+            'mail.message': {
+                fields: {},
+                records: [],
+            },
+            initMessaging: {
+                channel_slots: {
+                    channel_channel: [{
+                        id: 1,
+                        channel_type: "channel",
+                        name: "general",
+                    }],
+                },
+            },
+        };
+        this.services = mailTestUtils.getMailServices();
+        this.ORIGINAL_THREAD_WINDOW_APPENDTO = this.services.mail_service.prototype.THREAD_WINDOW_APPENDTO;
+
+        this.createParent = function (params) {
+            var widget = new Widget();
+
+            // in non-debug mode, append thread windows in qunit-fixture
+            // note that it does not hide thread window because it uses fixed
+            // position, and qunit-fixture uses absolute...
+            if (params.debug) {
+                self.services.mail_service.prototype.THREAD_WINDOW_APPENDTO = 'body';
+            } else {
+                self.services.mail_service.prototype.THREAD_WINDOW_APPENDTO = '#qunit-fixture';
+            }
+
+            testUtils.addMockEnvironment(widget, params);
+            return widget;
+        };
+    },
+    afterEach: function () {
+        // reset thread window append to body
+        this.services.mail_service.prototype.THREAD_WINDOW_APPENDTO = 'body';
+    },
+});
+
+QUnit.test('basic rendering thread window', function (assert) {
+    assert.expect(10);
+
+    var parent = this.createParent({
+        data: this.data,
+        services: this.services,
+    });
+
+    // detach channel 1, so that it opens corresponding thread window.
+    parent.call('mail_service', 'getChannel', 1).detach();
+
+    var $threadWindow = $('.o_thread_window');
+    assert.strictEqual($threadWindow.length, 1,
+        "thread window should be open");
+    assert.strictEqual($threadWindow.data('thread-id'), 1,
+        "thread window should be related to thread ID 1");
+
+    var $header = $threadWindow.find('.o_thread_window_header');
+    assert.strictEqual($header.length, 1,
+        "thread window should have a header");
+
+    var $title = $header.find('.o_thread_window_title');
+    assert.strictEqual($title.length, 1,
+        "thread window should have a title in the header");
+    assert.strictEqual($title.text().trim(), "#general",
+        "should have the title of the general channel");
+
+    var $buttons = $header.find('.o_thread_window_buttons');
+    assert.strictEqual($buttons.length, 1,
+        "should have buttons in the header of the thread window");
+    assert.strictEqual($buttons.find('.o_thread_window_expand').length, 1,
+        "should have a button to expand the thread window");
+    assert.strictEqual($buttons.find('.o_thread_window_close').length, 1,
+        "should have a button to close the thread window");
+
+    assert.strictEqual($threadWindow.find('.o_mail_thread').length, 1,
+        "should display the content of the general channel in the thread window");
+    assert.strictEqual($threadWindow.find('.o_thread_composer').length, 1,
+        "should display a composer in the thread window");
+
+    parent.destroy();
+});
+
+QUnit.test('close thread window using ESCAPE key', function (assert) {
+    assert.expect(5);
+
+    var parent = this.createParent({
+        data: this.data,
+        services: this.services,
+        mockRPC: function (route, args) {
+            if (args.method === 'channel_fold') {
+                assert.ok(true, "should call channel_fold");
+                return $.when();
+            }
+            return this._super.apply(this, arguments);
+        },
+    });
+
+    // get channel instance to link to thread window
+    var channel = parent.call('mail_service', 'getChannel', 1);
+    assert.ok(channel, "there should exist a channel locally with ID 1");
+
+    channel.detach();
+    assert.strictEqual($('.o_thread_window').length, 1,
+        "there should be a thread window that is opened");
+
+    // focus on the thread window and press ESCAPE
+    $('.o_thread_window .o_composer_text_field').click();
+    assert.strictEqual(document.activeElement,
+        $('.o_thread_window .o_composer_text_field')[0],
+        "thread window's input should now be focused");
+
+    var upKeyEvent = $.Event( "keyup", { which: 27 });
+    $('.o_thread_window .o_composer_text_field').trigger(upKeyEvent);
+
+    assert.strictEqual($('.o_thread_window').length, 0,
+        "the thread window should be closed");
+
+    parent.destroy();
+});
+
+QUnit.test('thread window\'s input can still be focused when the UI is blocked', function (assert) {
+    assert.expect(2);
+
+    var parent = this.createParent({
+        data: this.data,
+        services: this.services,
+    });
+
+    var $dom = $('#qunit-fixture');
+
+    // get channel instance to link to thread window
+    var channel = parent.call('mail_service', 'getChannel', 1);
+    channel.detach();
+
+    var $input = $('<input/>', {type: 'text'}).appendTo($dom);
+    $input.focus().click();
+    assert.strictEqual(document.activeElement, $input[0],
+        "fake input should be focused");
+
+    framework.blockUI();
+    // cannot force focus here otherwise the test
+    // makes no sense, this test is just about
+    // making sure that the code which forces the
+    // focus on click is not removed
+    $('.o_thread_window .o_composer_text_field').click();
+    assert.strictEqual(document.activeElement,
+        $('.o_thread_window .o_composer_text_field')[0],
+        "thread window's input should now be focused");
+
+    framework.unblockUI();
+    parent.destroy();
+});
+
+QUnit.test('emoji popover should open correctly in thread windows', function (assert) {
+    assert.expect(1);
+
+    var parent = this.createParent({
+        data: this.data,
+        services: this.services,
+    });
+
+    // get channel instance to link to thread window
+    var channel = parent.call('mail_service', 'getChannel', 1);
+    channel.detach();
+
+    var $emojiButton = $('.o_composer_button_emoji');
+    $emojiButton.trigger('focusin').focus().click();
+    var $popover = $('.o_mail_emoji_container');
+
+    var done = assert.async();
+    // Async is needed as the popover focusout hiding is deferred
+    setTimeout(function () {
+        assert.ok($popover.is(':visible'), "emoji popover should have stayed opened");
+        parent.destroy();
+        done();
+    }, 0);
+});
+
+QUnit.test('do not increase unread counter when receiving message with myself as author', function (assert) {
+    assert.expect(4);
+
+    var generalChannelID = 1;
+    var myselfPartnerID = 44;
+
+    this.data.initMessaging = {
+        channel_slots: {
+            channel_channel: [{
+                id: generalChannelID,
+                channel_type: 'channel',
+                name: "general",
+            }],
+        },
+    };
+
+    var parent = this.createParent({
+        data: this.data,
+        services: this.services,
+        session: { partner_id: myselfPartnerID }
+    });
+
+    // get channel instance to link to thread window
+    var channel = parent.call('mail_service', 'getChannel', 1);
+    channel.detach();
+
+    var threadWindowHeaderText = $('.o_thread_window_header').text().replace(/\s/g, "");
+
+    assert.strictEqual(threadWindowHeaderText, "#general",
+        "thread window header text should not have any unread counter initially");
+    assert.strictEqual(channel.getUnreadCounter(), 0,
+        "thread should have unread counter to 0 initially");
+
+    // simulate receiving message from myself
+    var messageData = {
+        author_id: [myselfPartnerID, "Myself"],
+        body: "<p>Test message</p>",
+        id: 2,
+        model: 'mail.channel',
+        res_id: 1,
+        channel_ids: [1],
+    };
+    var notification = [[false, 'mail.channel', generalChannelID], messageData];
+    parent.call('bus_service', 'trigger', 'notification', [notification]);
+
+    threadWindowHeaderText = $('.o_thread_window_header').text().replace(/\s/g, "");
+
+    assert.strictEqual(threadWindowHeaderText, "#general",
+        "thread window header text should not have any unread counter after receiving my message");
+    assert.strictEqual(channel.getUnreadCounter(), 0,
+        "thread should not have incremented its unread counter after receiving my message");
+
+    parent.destroy();
+});
+
+});
+});
+});
diff --git a/addons/mail/static/tests/thread_window/blank_thread_window_tests.js b/addons/mail/static/tests/thread_window/blank_thread_window_tests.js
new file mode 100644
index 00000000000..883494a4ec6
--- /dev/null
+++ b/addons/mail/static/tests/thread_window/blank_thread_window_tests.js
@@ -0,0 +1,318 @@
+odoo.define('mail.blankThreadWindowTests', function (require) {
+"use strict";
+
+var AbstractThreadWindow = require('mail.AbstractThreadWindow');
+var mailTestUtils = require('mail.testUtils');
+
+var testUtils = require('web.test_utils');
+var Widget = require('web.Widget');
+
+QUnit.module('mail', {}, function () {
+QUnit.module('Thread Window', {}, function () {
+QUnit.module('Blank', {
+    beforeEach: function () {
+        var self = this;
+
+        // define channel to link to chat window
+        this.data = {
+            'mail.message': {
+                fields: {},
+                records: [],
+            },
+            initMessaging: {
+                channel_slots: {
+                    channel_channel: [{
+                        id: 1,
+                        channel_type: "channel",
+                        name: "general",
+                    }],
+                },
+            },
+        };
+        this.services = mailTestUtils.getMailServices();
+        this.ORIGINAL_THREAD_WINDOW_APPENDTO = this.services.mail_service.prototype.THREAD_WINDOW_APPENDTO;
+
+        this.createParent = function (params) {
+            var widget = new Widget();
+
+            // in non-debug mode, append thread windows in qunit-fixture
+            // note that it does not hide thread window because it uses fixed
+            // position, and qunit-fixture uses absolute...
+            if (params.debug) {
+                self.services.mail_service.prototype.THREAD_WINDOW_APPENDTO = 'body';
+            } else {
+                self.services.mail_service.prototype.THREAD_WINDOW_APPENDTO = '#qunit-fixture';
+            }
+
+            testUtils.addMockEnvironment(widget, params);
+            return widget;
+        };
+
+        /**
+         * Patch autocomplete so that we can detect when 'source' or 'select'
+         * functions end.
+         *
+         * @param {Object} params
+         * @param {$.Deferred} params.selectDef
+         * @param {$.Deferred} params.sourceDef
+         */
+        this.patchAutocomplete = function (params) {
+            var selectDef = params.selectDef;
+            var sourceDef = params.sourceDef;
+            self.ORIGINAL_AUTOCOMPLETE = $.fn.autocomplete;
+            $.fn.autocomplete = function (params) {
+                var select = params.select;
+                var source = params.source;
+                params.select = function () {
+                    select.apply(this, arguments);
+                    selectDef.resolve();
+                };
+                params.source = function () {
+                    source.apply(this, arguments);
+                    sourceDef.resolve();
+                };
+                return self.ORIGINAL_AUTOCOMPLETE.apply(this, arguments);
+            };
+        };
+        /**
+         * Unpatch autocomplete
+         */
+        this.unpatchAutocomplete = function () {
+            $.fn.autocomplete = self.ORIGINAL_AUTOCOMPLETE;
+        };
+    },
+    afterEach: function () {
+        // reset thread window append to body
+        this.services.mail_service.prototype.THREAD_WINDOW_APPENDTO = 'body';
+    },
+});
+
+QUnit.test('basic rendering blank thread window', function (assert) {
+    assert.expect(5);
+
+    var parent = this.createParent({
+        data: this.data,
+        services: this.services,
+    });
+
+    // open blank thread window
+    parent.call('mail_service', 'openBlankThreadWindow');
+
+    assert.strictEqual($('.o_thread_window').length, 1,
+        "should have a thread window open");
+    assert.strictEqual($('.o_thread_window_title').text().trim(),
+        "New message",
+        "the blank window should have the correct title");
+    assert.strictEqual($('.o_composer_text_field').length, 0,
+        "should have no composer in the blank window");
+    assert.strictEqual($('.o_thread_search_input input').length, 1,
+        "the blank window should have an input");
+    assert.strictEqual($('.o_thread_search_input span').text().trim(),
+        "To:",
+        "the blank window should propose to type a partner next to the input");
+
+    parent.destroy();
+});
+
+QUnit.test('close blank thread window', function (assert) {
+    assert.expect(1);
+
+    var parent = this.createParent({
+        data: this.data,
+        services: this.services,
+    });
+
+    // open blank thread window
+    parent.call('mail_service', 'openBlankThreadWindow');
+
+    $('.o_thread_window_close').click();
+
+    assert.strictEqual($('.o_thread_window').length, 0,
+        "blank thread window should be closed");
+
+    parent.destroy();
+});
+
+QUnit.test('fold blank thread window', function (assert) {
+    // This test requires full height of thread windows when they are open.
+    // (e.g. 400px)
+    assert.expect(2);
+
+    var parent = this.createParent({
+        data: this.data,
+        services: this.services,
+    });
+
+    var HEIGHT_FOLDED = AbstractThreadWindow.prototype.HEIGHT_FOLDED;
+    var HEIGHT_OPEN = AbstractThreadWindow.prototype.HEIGHT_OPEN;
+
+    // Make fold animation instantaneous
+    testUtils.patch(AbstractThreadWindow, {
+        FOLD_ANIMATION_DURATION: 0,
+    });
+
+    // Open blank thread window
+    parent.call('mail_service', 'openBlankThreadWindow');
+    assert.strictEqual($('.o_thread_window').css('height'), HEIGHT_OPEN,
+        "blank thread window should be open");
+    if ($('.o_thread_window').css('height') !== HEIGHT_OPEN) {
+        console.warn('Assertion above may fail due to too narrow height of browser');
+    }
+
+    $('.o_thread_window_title').click();
+    assert.strictEqual($('.o_thread_window').css('height'), HEIGHT_FOLDED,
+        "blank thread window should be open");
+
+    parent.destroy();
+    testUtils.unpatch(AbstractThreadWindow);
+});
+
+QUnit.test('open new DM chat from blank thread window', function (assert) {
+    assert.expect(6);
+    var done = assert.async();
+
+    var self = this;
+    var selectDef = $.Deferred();
+    var sourceDef = $.Deferred();
+
+    this.patchAutocomplete({
+        selectDef: selectDef,
+        sourceDef: sourceDef,
+    });
+
+    var def = $.Deferred();
+
+    this.data['res.partner'] = {
+        fields: {},
+        records: [],
+    };
+
+    var parent = this.createParent({
+        data: this.data,
+        services: this.services,
+        mockRPC: function (route, args) {
+            if (args.method === 'im_search') {
+                def.resolve();
+                return $.when([
+                    { id: 1, name: 'DemoUser1' },
+                    { id: 2, name: 'DemoUser2', }
+                ]);
+            }
+            if (args.method === 'channel_get_and_minimize') {
+                return $.when({
+                    channel_type: 'chat',
+                    direct_partner: [{ id: args.args[0][0], name: 'DemoUser1', im_status: '' }],
+                    id: 50,
+                    is_minimized: true,
+                    name: 'DemoUser1',
+                });
+            }
+            return this._super.apply(this, arguments);
+        },
+    });
+
+    // open blank thread window
+    parent.call('mail_service', 'openBlankThreadWindow');
+
+    $('.o_thread_search_input input').val("D").trigger('keydown');
+
+    $.when(sourceDef, def).then(function () {
+        assert.strictEqual($('.ui-menu-item a').length, 2,
+            "should suggest 2 partners for DM");
+        assert.strictEqual($('.ui-menu-item a').eq(0).text(), "DemoUser1",
+            "first suggestion should be 'DemoUser1'");
+        assert.strictEqual($('.ui-menu-item a').eq(1).text(), "DemoUser2",
+            "second suggestion should be 'DemoUser2'");
+
+        $('.ui-menu-item a').eq(0).click();
+    });
+    selectDef.then(function () {
+        assert.strictEqual($('.o_thread_window').length, 1,
+            "should be a single window");
+        assert.strictEqual($('.o_thread_window_title').text().trim(), "#DemoUser1",
+            "should have thread window of the DM chat with 'DemoUser1'");
+        assert.strictEqual($('.o_composer_text_field').length, 1,
+            "should have a composer in the DM chat window");
+
+        self.unpatchAutocomplete();
+        parent.destroy();
+        done();
+    });
+});
+
+QUnit.test('open already detached DM chat from blank thread window', function (assert) {
+    // when opening an already detach DM chat from the blank thread window,
+    // the blank thread window should disappear
+    assert.expect(6);
+    var done = assert.async();
+
+    var self = this;
+    var selectDef = $.Deferred();
+    var sourceDef = $.Deferred();
+
+    this.patchAutocomplete({
+        selectDef: selectDef,
+        sourceDef: sourceDef,
+    });
+
+    var def = $.Deferred();
+
+    this.data['res.partner'] = {
+        fields: {},
+        records: [],
+    };
+    this.data.initMessaging.channel_slots.channel_dm = [{
+        channel_type: 'chat',
+        direct_partner: [{ id: 1, name: 'DemoUser1', im_status: '' }],
+        id: 50,
+        is_minimized: true,
+        name: 'DemoUser1',
+    }];
+
+    var parent = this.createParent({
+        data: this.data,
+        services: this.services,
+        mockRPC: function (route, args) {
+            if (args.method === 'im_search') {
+                def.resolve();
+                return $.when([
+                    { id: 1, name: 'DemoUser1' },
+                ]);
+            }
+            return this._super.apply(this, arguments);
+        },
+    });
+
+    assert.strictEqual($('.o_thread_window').length, 1,
+        "should be a single window");
+    assert.strictEqual($('.o_thread_window_title').text().trim(), "#DemoUser1",
+        "should have thread window of the DM chat with 'DemoUser1'");
+    assert.strictEqual($('.o_composer_text_field').length, 1,
+        "should have a composer in the DM chat window");
+
+    // open blank thread window
+    parent.call('mail_service', 'openBlankThreadWindow');
+
+    assert.strictEqual($('.o_thread_window').length, 2,
+        "should have two thread windows open");
+
+    $('.o_thread_search_input input').val("D").trigger('keydown');
+
+    $.when(sourceDef, def).then(function () {
+        $('.ui-menu-item a').eq(0).click();
+    });
+    selectDef.then(function () {
+        assert.strictEqual($('.o_thread_window').length, 1,
+            "should now have a single thread window open");
+        assert.strictEqual($('.o_thread_window_title').text().trim(), "#DemoUser1",
+            "the remaining thread window should be the DM chat with 'DemoUser1'");
+
+        self.unpatchAutocomplete();
+        parent.destroy();
+        done();
+    });
+});
+
+});
+});
+});
diff --git a/addons/mail/static/tests/thread_window/hidden_thread_window_tests.js b/addons/mail/static/tests/thread_window/hidden_thread_window_tests.js
new file mode 100644
index 00000000000..29e05c59da9
--- /dev/null
+++ b/addons/mail/static/tests/thread_window/hidden_thread_window_tests.js
@@ -0,0 +1,227 @@
+odoo.define('mail.hiddenThreadWindowTests', function (require) {
+"use strict";
+
+var mailTestUtils = require('mail.testUtils');
+
+var testUtils = require('web.test_utils');
+var Widget = require('web.Widget');
+
+QUnit.module('mail', {}, function () {
+QUnit.module('Thread Window', {}, function () {
+QUnit.module('Hidden', {
+    beforeEach: function () {
+        var self = this;
+
+        // define channel to link to chat window
+        this.data = {
+            'mail.message': {
+                fields: {},
+                records: [],
+            },
+            initMessaging: {
+                channel_slots: {
+                    channel_channel: [{
+                        id: 1,
+                        channel_type: "channel",
+                        name: "general",
+                    }],
+                },
+            },
+        };
+        this.services = mailTestUtils.getMailServices();
+        this.ORIGINAL_THREAD_WINDOW_APPENDTO = this.services.mail_service.prototype.THREAD_WINDOW_APPENDTO;
+
+        this.createParent = function (params) {
+            var widget = new Widget();
+
+            // in non-debug mode, append thread windows in qunit-fixture
+            // note that it does not hide thread window because it uses fixed
+            // position, and qunit-fixture uses absolute...
+            if (params.debug) {
+                self.services.mail_service.prototype.THREAD_WINDOW_APPENDTO = 'body';
+            } else {
+                self.services.mail_service.prototype.THREAD_WINDOW_APPENDTO = '#qunit-fixture';
+            }
+
+            testUtils.addMockEnvironment(widget, params);
+            return widget;
+        };
+    },
+    afterEach: function () {
+        // reset thread window append to body
+        this.services.mail_service.prototype.THREAD_WINDOW_APPENDTO = 'body';
+    },
+});
+
+QUnit.test('hidden thread windows dropdown when not enough horizontal space (version 1)', function (assert) {
+    // This test has hard-set global width, so that it does not depend on
+    // the width of the screen: at most 2 thread windows visible at the
+    // same time, and additional thread windows are in hidden while and
+    // still showing 2 visible thread windows. It assumes that the width
+    // of the 'hidden thread window' button is less than the width of a
+    // single thread window.
+    assert.expect(13);
+
+    testUtils.patch(this.services.mail_service, {
+        HIDDEN_THREAD_WINDOW_DROPDOWN_BUTTON_WIDTH: 100,
+        THREAD_WINDOW_WIDTH: 300,
+        _getGlobalWidth: function () { return 800; },
+    });
+
+    var channels = [];
+    for (var i = 0; i < 3; i++) {
+        channels.push({
+            id: i,
+            channel_type: 'channel',
+            name: "channel" + i,
+        });
+    }
+
+    this.data.initMessaging = {
+        channel_slots: {
+            channel_channel: channels,
+        },
+    };
+
+    var parent = this.createParent({
+        data: this.data,
+        services: this.services,
+    });
+
+    parent.call('mail_service', 'getChannel', 0).detach();
+    parent.call('mail_service', 'getChannel', 1).detach();
+
+    var $visibleThreadWindows = $('.o_thread_window:not(.o_thread_window_dropdown, .o_hidden)');
+
+    assert.strictEqual($visibleThreadWindows.length, 2,
+        "should have 2 thread windows visible (as many as available slots)");
+    assert.strictEqual($visibleThreadWindows.filter('[data-thread-id="0"]').length, 1,
+        "the thread window with ID 0 should be visible");
+    assert.strictEqual($visibleThreadWindows.filter('[data-thread-id="1"]').length, 1,
+        "the thread window with ID 1 should be visible");
+    assert.strictEqual($('.o_thread_window.o_hidden').length, 0,
+        "there should be no hidden thread when less or exactly as many as available slots");
+    assert.strictEqual($('.o_thread_window_dropdown').length, 0,
+        "there should be no thread window dropdown when all thread windows are visible");
+
+    // detach a channel so that it exceeds available slots
+    parent.call('mail_service', 'getChannel', 2).detach();
+    // update list of visible thread windows
+    $visibleThreadWindows = $('.o_thread_window:not(.o_thread_window_dropdown, .o_hidden)');
+
+    assert.strictEqual($visibleThreadWindows.length, 2,
+        "should have as many thread window visible as available slots");
+    assert.strictEqual($visibleThreadWindows.filter('[data-thread-id="0"]').length, 1,
+        "the thread window with ID 0 should be visible");
+    assert.strictEqual($visibleThreadWindows.filter('[data-thread-id="2"]').length, 1,
+        "the thread window with ID 2 should be visible (swapped with ID 1)");
+    assert.strictEqual($('.o_thread_window.o_hidden').length, 1,
+        "there should be a hidden thread when more windows than available slots");
+    assert.strictEqual($('.o_thread_window.o_hidden').data('thread-id'), 1,
+        "hidden thread window should be thread window with ID 1 (swapped with ID 2)");
+    var $hiddenDropdown = $('.o_thread_window_dropdown');
+    assert.strictEqual($hiddenDropdown.length, 1,
+        "there should be a thread window dropdown");
+    assert.strictEqual($('.o_thread_window_dropdown_toggler').text().trim(), "1",
+        "should display that there is one hidden thread window");
+    assert.strictEqual($hiddenDropdown.find('.o_thread_window_header[data-thread-id="1"]').length,
+        1, "should contain thread window with ID 1 in hidden dropdown menu");
+
+    parent.destroy();
+    testUtils.unpatch(this.services.mail_service);
+});
+
+QUnit.test('hidden thread windows dropdown when not enough horizontal space (version 2)', function (assert) {
+    // This is almost the same test as the one before, except there are
+    // at most 3 thread windows visible, and 2 thread windows are visible
+    // when it shows the 'hidden thread window' button.
+    // This case occurs when the amount of available slots depends on
+    // whether the hidden button should be displayed or not
+    // Example:
+    //      - global width of 800px
+    //      - button width of 100px
+    //      - thread width of 250px
+    //
+    // Without button: 3 thread windows (3*250px = 750px < 800px)
+    //    With button: 2 thread windows (2*250px + 100px = 600px < 800px)
+    assert.expect(16);
+
+    testUtils.patch(this.services.mail_service, {
+        HIDDEN_THREAD_WINDOW_DROPDOWN_BUTTON_WIDTH: 100,
+        THREAD_WINDOW_WIDTH: 250,
+        _getGlobalWidth: function () { return 800; },
+    });
+
+    var channels = [];
+    for (var i = 0; i < 4; i++) {
+        channels.push({
+            id: i,
+            channel_type: 'channel',
+            name: "channel" + i,
+        });
+    }
+
+    this.data.initMessaging = {
+        channel_slots: {
+            channel_channel: channels,
+        },
+    };
+
+    var parent = this.createParent({
+        data: this.data,
+        services: this.services,
+    });
+
+    parent.call('mail_service', 'getChannel', 0).detach();
+    parent.call('mail_service', 'getChannel', 1).detach();
+    parent.call('mail_service', 'getChannel', 2).detach();
+
+    var $visibleThreadWindows = $('.o_thread_window:not(.o_thread_window_dropdown, .o_hidden)');
+
+    assert.strictEqual($visibleThreadWindows.length, 3,
+        "should have 3  thread windows visible (as many as available slots)");
+    assert.strictEqual($visibleThreadWindows.filter('[data-thread-id="0"]').length, 1,
+        "the thread window with ID 0 should be visible");
+    assert.strictEqual($visibleThreadWindows.filter('[data-thread-id="1"]').length, 1,
+        "the thread window with ID 1 should be visible");
+    assert.strictEqual($visibleThreadWindows.filter('[data-thread-id="2"]').length, 1,
+        "the thread window with ID 2 should be visible");
+    assert.strictEqual($('.o_thread_window.o_hidden').length, 0,
+        "there should be no hidden thread when exactly as many as available slots");
+    assert.strictEqual($('.o_thread_window_dropdown').length, 0,
+        "there should be no thread window dropdown when all thread windows are visible");
+
+    // detach a channel so that it exceeds available slots
+    parent.call('mail_service', 'getChannel', 3).detach();
+    // update list of visible thread windows
+    $visibleThreadWindows = $('.o_thread_window:not(.o_thread_window_dropdown, .o_hidden)');
+
+    assert.strictEqual($visibleThreadWindows.length, 2,
+        "should have 2 thread windows visible (as many as available slots)");
+    assert.strictEqual($visibleThreadWindows.filter('[data-thread-id="0"]').length, 1,
+        "the thread window with ID 0 should be visible");
+    assert.strictEqual($visibleThreadWindows.filter('[data-thread-id="3"]').length, 1,
+        "the thread window with ID 3 should be visible (swapped with IDs 1 and 2)");
+    assert.strictEqual($('.o_thread_window.o_hidden').length, 2,
+        "there should be two hidden thread when more windows than available slots");
+    assert.strictEqual($('.o_thread_window.o_hidden[data-thread-id="1"]').length, 1,
+        "thread window with ID 1 should be hidden");
+    assert.strictEqual($('.o_thread_window.o_hidden[data-thread-id="2"]').length, 1,
+        "thread window with ID 2 should be hidden");
+    var $hiddenDropdown = $('.o_thread_window_dropdown');
+    assert.strictEqual($hiddenDropdown.length, 1,
+        "there should be a thread window dropdown");
+    assert.strictEqual($('.o_thread_window_dropdown_toggler').text().trim(), "2",
+        "should display that there is 2 hidden thread windows");
+    assert.strictEqual($hiddenDropdown.find('.o_thread_window_header[data-thread-id="1"]').length,
+        1, "should contain thread window with ID 1 in hidden dropdown menu");
+    assert.strictEqual($hiddenDropdown.find('.o_thread_window_header[data-thread-id="2"]').length,
+        1, "should contain thread window with ID 2 in hidden dropdown menu");
+
+    parent.destroy();
+    testUtils.unpatch(this.services.mail_service);
+});
+
+});
+});
+});