How to test throwing error from module root (not method) - jestjs

Question

We have module within there is some initial logic which test that some value was configured, if not, it throws error.. then also the module provides methods. I want to describe this in specification (test), using Jest framework and test the feature. Here is simplified reproduced example:
// dependency.service.ts
export const something = {
method() {
return "methodValue";
}
};
export default function somethingElse() {
return "somethingElseValue";
}
// index.ts
import somethingElse, { something } from "./dependency.service";
const value1 = somethingElse();
const value2 = something.method();
console.log("ROOT somethingElse", value1);
console.log("ROOT something.method", value2);
// initialisation of module fails
if(value1 === 'throw_error' || value2 === 'throw_error') {
throw 'Some error';
}
export function smElse() {
const value = somethingElse();
console.log("somethingElse", value);
return value;
}
export function smMethod() {
const value = something.method();
console.log("somethingElse", value);
return value;
}
// index.spec.ts
import { smElse, smMethod } from './index';
jest.mock('./dependency.service', () => ({
__esModule: true,
default: jest.fn(() => 'MOCKED_somethingElseValue'),
something: {
method: jest.fn(() => 'MOCKED_methodValue'),
},
}));
describe('index', () => {
// some tests for happy paths
it('smElse returns mocked value', () => {
expect(smElse()).toMatchInlineSnapshot(`"MOCKED_somethingElseValue"`);
});
it('smMethod returns mocked value', () => {
expect(smMethod()).toMatchInlineSnapshot(`"MOCKED_methodValue"`);
});
it('smElse returns per test mocked value', () => {
const somethingElseMocked = require('./dependency.service').default;
somethingElseMocked.mockReturnValueOnce('ANOTHER_MOCKED_somethingElseValue');
expect(smElse()).toMatchInlineSnapshot(`"ANOTHER_MOCKED_somethingElseValue"`);
});
it('smMethod returns per test mocked value', () => {
const something = require('./dependency.service').something;
something.method.mockReturnValueOnce('ANOTHER_MOCKED_methodValue');
expect(smMethod()).toMatchInlineSnapshot(`"ANOTHER_MOCKED_methodValue"`);
});
// this is testing the throwing error in module root
it('throws error when somethingElse returns specific message', () => {
expect.assertions(1);
jest.isolateModules(() => {
const somethingElseMocked = require('./dependency.service').default;
somethingElseMocked.mockReturnValueOnce('throw_error');
try {
require('./index');
} catch (error) {
expect(error).toBe("Some error");
}
});
});
it('throws error when something.method returns specific message', () => {
expect.assertions(1);
jest.isolateModules(() => {
const somethingMethodMocked = require('./dependency.service').something.method;
somethingMethodMocked.mockReturnValueOnce('throw_error');
try {
require('./index');
} catch (error) {
expect(error).toBe("Some error");
}
});
});
});
"Try catch in isolation" solution does not work with async code as isolateModules method does not support async functions yet, reference: https://github.com/facebook/jest/issues/10428. I need alternative solution which would support async code.
Whole reproduced example repo here: https://github.com/luckylooke/jestTestModuleRootThrow/tree/main
EDIT:
I found out that some asynchronicity is supported by isolateModules, at least my use case, once I used expect.assertions(1) following test works as expected:
it('throws error when token data are not valid', async () => {
expect.assertions(1);
jest.isolateModules(async () => {
require('crypto-package').someMethod.mockReturnValueOnce(Promise.resolve({
decoderMethod: () => Promise.resolve('{ broken data }'),
}));
const { getTokenData } = require("./decoder.service");
await expect(getTokenData('34534xxxxxxxxxxxxxxx12628')).rejects.toMatchInlineSnapshot(`"Invalid token data"`);
});
});