Port spec/javascripts/behaviors/copy_as_gfm_spec.js to Jest

spec/frontend/behaviors/copy_as_gfm_spec.js

+import $ from 'jquery';
+import initCopyAsGFM, { CopyAsGFM } from '~/behaviors/markdown/copy_as_gfm';
+import { setHTMLFixture } from 'helpers/fixtures';
+
+describe('CopyAsGFM', () => {
+  describe('initCopyAsGFM', () => {
+    beforeEach(() => {
+      jest.spyOn(CopyAsGFM, 'copyAsGFM').mockImplementation(() => {});
+      jest.spyOn(CopyAsGFM, 'pasteGFM').mockImplementation(() => {});
+      setHTMLFixture(`
+        <div class="md"></div>
+        <div class="wiki"></div>
+        <pre class="code highlight"></pre>
+        <div class="diff-content"><div class="line_content"></div></div>
+        <div class="js-gfm-input"></div>
+      `);
+
+      initCopyAsGFM();
+    });
+
+    afterEach(() => {
+      $(document).off('copy');
+      $(document).off('paste');
+    });
+
+    it.each`
+      selector                         | expectedTransform
+      ${'.md'}                         | ${CopyAsGFM.transformGFMSelection}
+      ${'.wiki'}                       | ${CopyAsGFM.transformGFMSelection}
+      ${'pre.code.highlight'}          | ${CopyAsGFM.transformCodeSelection}
+      ${'.diff-content .line_content'} | ${CopyAsGFM.transformCodeSelection}
+    `(
+      'calls copyAsGFM with $expectedTransform.name for copy event on $selector',
+      ({ selector, expectedTransform }) => {
+        const copyEvent = $.Event('copy');
+        const $element = $(selector);
+        expect($element.length).toBe(1);
+
+        $element.trigger(copyEvent);
+
+        expect(CopyAsGFM.copyAsGFM).toHaveBeenCalledWith(copyEvent, expectedTransform);
+      },
+    );
+
+    it('calls pasteGFM for paste event on .js-gfm-input', () => {
+      const pasteEvent = $.Event('paste');
+      const $element = $('.js-gfm-input');
+      expect($element.length).toBe(1);
+
+      $element.trigger(pasteEvent);
+
+      expect(CopyAsGFM.pasteGFM).toHaveBeenCalledWith(pasteEvent);
+    });
+  });
+});