Tests for keyboard shortcuts in native editor (microsoft#7797)

* Tests for keyboard shortcuts * Added some more tests * Code review comments * Fix merge issues

Author: DonJayamanne

src/datascience-ui/interactive-common/cellOutput.tsx

@@ -174,7 +174,7 @@ export class CellOutput extends React.Component<ICellOutputProps> {
  const Transform = transforms['text/markdown'];
  const MarkdownClassName = 'markdown-cell-output';
 
- return [<div className={MarkdownClassName}><Transform key={0} data={source} /></div>];
+ return [<div key={0} className={MarkdownClassName}><Transform key={0} data={source} /></div>];
  }
 
  // tslint:disable-next-line: max-func-body-length

src/datascience-ui/react-common/monacoEditor.tsx

@@ -33,7 +33,7 @@ export interface IMonacoEditorProps {
  lineCountChanged(newCount: number): void;
 }
 
-interface IMonacoEditorState {
+export interface IMonacoEditorState {
  editor?: monacoEditor.editor.IStandaloneCodeEditor;
  model: monacoEditor.editor.ITextModel | null;
  visibleLineCount: number;