How to use the @jupyterlab/testutils.NBTestUtils.createCodeCellFactory function in @jupyterlab/testutils

describe('CodeCell', () => {
    const contentFactory = NBTestUtils.createCodeCellFactory();
    const model = new CodeCellModel({});

    describe('#constructor()', () => {
      it('should create a code cell widget', () => {
        const widget = new CodeCell({ model, rendermime, contentFactory });
        widget.initializeState();
        expect(widget).toBeInstanceOf(CodeCell);
      });

      it('should accept a custom contentFactory', () => {
        const contentFactory = NBTestUtils.createCodeCellFactory();
        const widget = new CodeCell({ model, contentFactory, rendermime });
        widget.initializeState();
        expect(widget).toBeInstanceOf(CodeCell);
      });
    });

it('should add a code cell to the content widget', () => {
        const contentFactory = NBTestUtils.createCodeCellFactory();
        const model = new CodeCellModel({});
        const cell = new CodeCell({
          model,
          contentFactory,
          rendermime
        }).initializeState();
        Widget.attach(widget, document.body);
        expect(widget.cells.length).to.equal(0);
        widget.addCell(cell);
        expect(widget.cells.length).to.equal(1);
      });
    });

it('should add a code cell to the content widget', () => {
        const contentFactory = NBTestUtils.createCodeCellFactory();
        const model = new CodeCellModel({});
        const cell = new CodeCell({
          model,
          contentFactory,
          rendermime
        }).initializeState();
        Widget.attach(widget, document.body);
        expect(widget.cells.length).to.equal(0);
        widget.addCell(cell);
        expect(widget.cells.length).to.equal(1);
      });
    });

it('should accept a custom contentFactory', () => {
        const contentFactory = NBTestUtils.createCodeCellFactory();
        const widget = new CodeCell({ model, contentFactory, rendermime });
        widget.initializeState();
        expect(widget).toBeInstanceOf(CodeCell);
      });
    });

it('should add a code cell to the content widget', () => {
        const contentFactory = NBTestUtils.createCodeCellFactory();
        const model = new CodeCellModel({});
        const cell = new CodeCell({
          model,
          contentFactory,
          rendermime
        }).initializeState();
        Widget.attach(widget, document.body);
        expect(widget.cells.length).to.equal(0);
        widget.addCell(cell);
        expect(widget.cells.length).to.equal(1);
      });
    });

constructor() {
    super({
      model: new CodeCellModel({}),
      contentFactory: NBTestUtils.createCodeCellFactory(),
      rendermime
    });
  }

createCodeCell(): CodeCell {
    const contentFactory = NBTestUtils.createCodeCellFactory();
    const model = new CodeCellModel({});
    const cell = new CodeCell({
      model,
      rendermime,
      contentFactory
    }).initializeState();
    return cell;
  }

createCodeCell(): CodeCell {
    const contentFactory = NBTestUtils.createCodeCellFactory();
    const model = new CodeCellModel({});
    const cell = new CodeCell({
      model,
      rendermime,
      contentFactory
    }).initializeState();
    return cell;
  }

constructor() {
    super({
      model: new CodeCellModel({}),
      contentFactory: NBTestUtils.createCodeCellFactory(),
      rendermime
    });
  }