Migrate blob_file_dropzone to jest

spec/javascripts/blob/blob_file_dropzone_spec.js → spec/frontend/blob/blob_file_dropzone_spec.js

 import $ from 'jquery';
 import BlobFileDropzone from '~/blob/blob_file_dropzone';
 
-describe('BlobFileDropzone', function() {
+describe('BlobFileDropzone', () => {
   preloadFixtures('blob/show.html');
+  let dropzone;
+  let replaceFileButton;
+  const jQueryMock = {
+    enable: jest.fn(),
+    disable: jest.fn(),
+  };
 
   beforeEach(() => {
     loadFixtures('blob/show.html');
     const form = $('.js-upload-blob-form');
-    this.blobFileDropzone = new BlobFileDropzone(form, 'POST');
-    this.dropzone = $('.js-upload-blob-form .dropzone').get(0).dropzone;
-    this.replaceFileButton = $('#submit-all');
+    // eslint-disable-next-line no-new
+    new BlobFileDropzone(form, 'POST');
+    dropzone = $('.js-upload-blob-form .dropzone').get(0).dropzone;
+    dropzone.processQueue = jest.fn();
+    replaceFileButton = $('#submit-all');
+    $.fn.extend(jQueryMock);
   });
 
   describe('submit button', () => {
     it('requires file', () => {
-      spyOn(window, 'alert');
+      jest.spyOn(window, 'alert').mockImplementation(() => {});
 
-      this.replaceFileButton.click();
+      replaceFileButton.click();
 
       expect(window.alert).toHaveBeenCalled();
     });
 
     it('is disabled while uploading', () => {
-      spyOn(window, 'alert');
+      jest.spyOn(window, 'alert').mockImplementation(() => {});
 
       const file = new File([], 'some-file.jpg');
       const fakeEvent = $.Event('drop', {
         dataTransfer: { files: [file] },
       });
 
-      this.dropzone.listeners[0].events.drop(fakeEvent);
-      this.replaceFileButton.click();
+      dropzone.listeners[0].events.drop(fakeEvent);
+
+      replaceFileButton.click();
 
       expect(window.alert).not.toHaveBeenCalled();
-      expect(this.replaceFileButton.is(':disabled')).toEqual(true);
+      expect(jQueryMock.enable).toHaveBeenCalled();
+      expect(dropzone.processQueue).toHaveBeenCalled();
     });
   });
 });