How to mock export default function-CodePudding

//MyConfig.ts
export default function getConfig(name: string): string {
  // do some logic
  return var;
}

//MyUtil.ts
import getConfig from './MyConfig';

export default class MyUtil {
  public static isFoo(): boolean {
    const config = getConfig();
    return config == 'Foo';
  }
}

//MyUtil.test.ts
import MyUtil from '../MyUtil';
import * as config from '../MyConfig';

const configMock = config.default as jest.Mock;

describe('tests', () => {
  it('blah', async () => {
    configMock.mockReturnValue('mock-config');
    const foo = MyUtil.isFoo();
  });
});

I tried to mock getConfg function from MyConfig.ts in MyUtil.test.ts. I am getting an error 'configMock.mockReturnValue is not a function'.

How do I mock the export default function?

CodePudding user response：

You can use the direct function and assign the value in the spec file. Like

configMock = () => return 'mockConfig';

you don't need to use mockReturnValue for that case. Thanks.

CodePudding user response：

You will need to call jest.mock('../MyConfig') in your test code.

See the jest documentation: https://jestjs.io/docs/mock-functions#mocking-modules

//MyUtil.test.ts
import MyUtil from '../MyUtil';
import * as config from '../MyConfig';

jest.mock('../MyConfig')

describe('tests', () => {
  it('blah', async () => {
    config.default.mockReturnValue('mock-config');
    const foo = MyUtil.isFoo();
  });
});