MAGETWO-54733: Unable to save product with all unchecked values for m…

…ultiple select attribute #7687

app/code/Magento/Ui/view/base/web/js/form/element/multiselect.js

@@ -41,8 +41,14 @@ define([
             return _.isString(value) ? value.split(',') : value;
         },
 
+        /**
+         * Sets the prepared data to dataSource
+         * by path, where key is component link to dataSource with
+         * suffix "-prepared-for-send"
+         *
+         * @param {Array} data - current component value
+         */
         setPrepareToSendData: function (data) {
-
             if (!data.length) {
                 data = '';
             }

dev/tests/js/jasmine/tests/app/code/Magento/Ui/base/js/form/element/multiselect.test.js

@@ -0,0 +1,60 @@
+/**
+ * Copyright © 2013-2017 Magento, Inc. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+
+/* eslint max-nested-callbacks: 0 */
+define([
+    'squire'
+], function (Squire) {
+    'use strict';
+
+    var injector = new Squire(),
+        mocks = {
+            'Magento_Ui/js/lib/core/events': {
+                on: jasmine.createSpy()
+            },
+            'Magento_Ui/js/lib/registry/registry': {
+                get: function() {
+                    return {
+                        get: jasmine.createSpy(),
+                        set: jasmine.createSpy()
+                    };
+                },
+                create: jasmine.createSpy(),
+                set: jasmine.createSpy(),
+                async: jasmine.createSpy()
+            },
+            '/mage/utils/wrapper': jasmine.createSpy()
+        },
+        obj,
+        dataScope = 'dataScope';
+
+    beforeEach(function (done) {
+        injector.mock(mocks);
+        injector.require(['Magento_Ui/js/form/element/multiselect'], function (Constr) {
+            obj = new Constr({
+                provider: 'provName',
+                name: '',
+                index: '',
+                dataScope: dataScope
+            });
+
+            done();
+        });
+    });
+
+    describe('Magento_Ui/js/form/element/multiselect', function () {
+        describe('"setPrepareToSendData" method', function () {
+            it('Check method call with empty array as parameter.', function () {
+                expect(obj.setPrepareToSendData([])).toBeUndefined();
+                expect(obj.source.set).toHaveBeenCalledWith(dataScope + '-prepared-for-send', '');
+            });
+
+            it('Check method call with array with data as parameter.', function () {
+                expect(obj.setPrepareToSendData(['1', '2', '3'])).toBeUndefined();
+                expect(obj.source.set).toHaveBeenCalledWith(dataScope + '-prepared-for-send', ['1', '2', '3']);
+            });
+        });
+    });
+});