Svelte - Not able to fetch data from JSON file during jest unit testing

Question

During unit testing, I am getting undefined error, while executing svelte component with json file.

Restaurant.svelte :

import data from '../Data/restaurants.json';
console.log(data);
let finalData = data.restaurants;

restaurant.spec.js :

import Restaurant from './../routes/Restaurant.svelte';
import { render, screen, fireEvent } from "@testing-library/svelte";


describe("Restaurants Home Page",()=>{
    it("Tests for Header",()=>{
        render(Restaurant);
        const resheader = screen.getByText("Restaurants");
        expect(resheader).toBeVisible();
    })
})

Jest Config File :

{
    "transform": {
      "^.+\\.js$": "babel-jest",
      "^.+\\.svelte$": "svelte-jester",
      ".+\\.(css|styl|less|sass|scss|png|jpg|ttf|woff|woff2)$": "jest-transform-stub"
    },
    "moduleFileExtensions": ["svelte", "js", "json"],
    "transformIgnorePatterns": ["node_modules/(?!(svelte-spa-router|svelte-i18n)/)"],
    "testEnvironment": "jsdom",
    "setupFilesAfterEnv": ["@testing-library/jest-dom/extend-expect"],
    "moduleDirectories": [
      "node_modules",
      "src"
    ],
    "moduleNameMapper": {
      "src/(.*)": "<rootDir>/src/Data"
    }    
}

Error Msg: TypeError: Cannot read properties of undefined (reading 'restaurants')

   7 |
   8 |     console.log(data);
>  9 |     let finalData = data.restaurants;

Answer 1

I highly recommend using vitest for testing SvelteKit apps as they both use vite which reduces the amount of configuration and incompatibilities.

That said, this can also work in svelte-jester by using the * as syntax:

import * as data from "../data/restaurants.json";