Issue using GridStack with Jest tests

[SriSindhuMallela]

Hi, I'm using GridStack in my angular application, it works great for the actual scenario but i'm facing problem with unit tests setup with jest framework. Below is the screenshot of the error and I tried various things like setting transform and transformIgnorePatterns in jest config but it didn't work.

Jest encountered an unexpected token
    
Jest failed to parse a file. This happens e.g. when your code or its dependencies use non-standard JavaScript syntax, or when Jest is not configured to support such syntax.

    Out of the box Jest supports Babel, which will be used to transform your files into valid JS based on your Babel configuration.

    By default "node_modules" folder is ignored by transformers.

    Here's what you can do:
     • If you are trying to use ECMAScript Modules, see https://jestjs.io/docs/ecmascript-modules for how to enable it.
     • If you are trying to use TypeScript, see https://jestjs.io/docs/getting-started#using-typescript
     • To have some of your "node_modules" files transformed, you can specify a custom "transformIgnorePatterns" in your config.
     • If you need a custom transformation specify a "transform" option in your config.
     • If you simply want to mock your non-JS modules (e.g. binary assets) you can stub them out with the "moduleNameMapper" config option.

    You'll find more details and examples of these config options in the docs:
    https://jestjs.io/docs/configuration
    For information about custom transformations, see:
    https://jestjs.io/docs/code-transformation

    Details:

    .../node_modules/gridstack/dist/gridstack.js:8
    import { GridStackEngine } from './gridstack-engine';
    ^^^^^^

    SyntaxError: Cannot use import statement outside a module

    > 12 | import { GridStack, GridStackOptions, GridStackWidget } from 'gridstack';
         | ^
      
      at Runtime.createScriptFromCode (node_modules/jest-runtime/build/index.js:1505:14)
      at Object.require (src/app/modules/home/home-page/home-page.component.ts:12:1)
      at Object.<anonymous> (src/app/modules/home/home-page/home-page.component.spec.ts:2:1)

Highly appreciate any inputs on how to fix this issue?

[wall-street-dev]

You need to mock it.
This should get you started:

const eventEmitterTrigger$ = new Subject<string>();
const registry: GridStackElement[] = [];
jest.mock('gridstack', () => ({
    GridStack: {
        ...jest.requireActual('gridstack'),
        init: () => ({
            on: (name: GridStackEvent, callback: GridStackEventHandlerCallback): void => {
                eventEmitterTrigger$.subscribe(eventName => {
                    (callback as GridStackEventHandler)(new Event(eventName));
                });
            },
            off: jest.fn(),
            setStatic: jest.fn(),
            getGridItems: () => registry,
            addWidget: (item: GridStackElement) => {
                registry.push(item);
            },
            removeWidget: jest.fn(),
            destroy: jest.fn()
        })
    }
}));