Jest : Mock import of JSON file

Question

I am currently testing one of my React component like this:

it('renders correctly', () => {   const tree = renderer.create(<Scene {...props} />).toJSON();   expect(tree).toMatchSnapshot(); }); 

My component Scene imports a setting.json file. I have that file on my local instance, but I do not push it on my CI instance. So when it tries to import it, the file is not found.

Is there a way to mock this file in my test ?

Answer 1

You can either use moduleNameMapper in your jest settings to point the import to an mocked json file.

{   "moduleNameMapper": {     "setting.json": "<rootDir>/__mocks__/setting.json"   } } 

Or you can use jest.mock inside your test to mock the file directly, note that you have to add the { virtual: true } parameter.

jest.mock('path/to/setting.json', ()=>({   settings: 'someSetting' }), { virtual: true }) 

Answer 2

For those looking to mock JSON in the form of an Array, just return an array from the callback.

jest.mock('./data.json', () => ([1, 2, 3])); 

You can return other valid JSON types as well: Object, String, Number, Boolean, or Null.