Added specs to util methods

spec/frontend/emoji/components/utils_spec.js

+import Cookies from 'js-cookie';
+import { getFrequentlyUsedEmojis, addToFrequentlyUsed } from '~/emoji/components/utils';
+
+jest.mock('js-cookie');
+
+describe('getFrequentlyUsedEmojis', () => {
+  it('it returns null when no saved emojis set', () => {
+    jest.spyOn(Cookies, 'get').mockReturnValue(null);
+
+    expect(getFrequentlyUsedEmojis()).toBe(null);
+  });
+
+  it('it returns frequently used emojis object', () => {
+    jest.spyOn(Cookies, 'get').mockReturnValue('thumbsup,thumbsdown');
+
+    expect(getFrequentlyUsedEmojis()).toEqual({
+      frequently_used: {
+        emojis: [['thumbsup', 'thumbsdown']],
+        top: 0,
+        height: 71,
+      },
+    });
+  });
+});
+
+describe('addToFrequentlyUsed', () => {
+  it('sets cookie value', () => {
+    jest.spyOn(Cookies, 'get').mockReturnValue(null);
+
+    addToFrequentlyUsed('thumbsup');
+
+    expect(Cookies.set).toHaveBeenCalledWith('frequently_used_emojis', 'thumbsup', {
+      expires: 365,
+    });
+  });
+
+  it('sets cookie value to include previously set cookie value', () => {
+    jest.spyOn(Cookies, 'get').mockReturnValue('thumbsdown');
+
+    addToFrequentlyUsed('thumbsup');
+
+    expect(Cookies.set).toHaveBeenCalledWith('frequently_used_emojis', 'thumbsdown,thumbsup', {
+      expires: 365,
+    });
+  });
+
+  it('sets cookie value with uniq values', () => {
+    jest.spyOn(Cookies, 'get').mockReturnValue('thumbsup');
+
+    addToFrequentlyUsed('thumbsup');
+
+    expect(Cookies.set).toHaveBeenCalledWith('frequently_used_emojis', 'thumbsup', {
+      expires: 365,
+    });
+  });
+});