jest.mock(..) not working in 'describe' (TypeError: moduleName.split is not a function) - jestjs

Question

jest.mock(..) does not seem to work at the 'describe' level for my tests.
If I have the following :
import React from 'react';
import {someFunction} from "./something/someFile";
describe('Overview Test', () => {
jest.mock(someFunction);
test(' snapshot', () => {
});
});
Then running the 'test' (ie. at the test level), works fine.
But if I run the 'describe' (ie. the describe level or suite level), then I get the following error :
TypeError: moduleName.split is not a function
at Resolver.resolveModuleFromDirIfExists (A:\frontend\node_modules\jest-resolve\build\index.js:224:30)
at Resolver.resolveModule (A:\frontend\node_modules\jest-resolve\build\index.js:252:12)
If I have this :
describe('Overview Test', () => {
test(' snapshot', () => {
jest.mock(someFunction);
});
});
Then both ways it does not work.
I have also tried this :
import React from 'react';
import {someFunction} from "./something/someFile";
describe('Overview Test', () => {
beforeEach(() => {
jest.mock(someFunction);
});
test(' snapshot', () => {
});
});
And it does not work.
UPDATE
I have also tried this and it does not work :
import React from 'react';
import {someFunction} from "./something/someFile";
describe('Overview Test', () => {
jest.mock('./something/someFile', () => {
return { someFunction: jest.fn(() => "futhissit")};
});
test(' snapshot', () => {
someFunction()
});
});

Answer 1

Jest mock is for mocking modules and the first argument is the moduleName which it has to be a valid module name (inside node_modules or a file path) and not a direct function/module:
jest.mock(moduleName, factory, options)
Mocks a module with an auto-mocked version when it is being required. factory and options are optional.
The error you're getting TypeError: moduleName.split is not a function is because resolveModuleFromDirIfExists tries to split the module name/path and you can see it inside jest-resolve/src/index.ts at line 207.
When you want to test an ES module, you pass the module location for the moduleName and you create a factory using __esModule: true and then create properties with exported functions being mocked using jest.fn():
someFile.js exports the someFunction:
module.exports.someFunction = () => 'Some function result!';
Mocking someFile.js module using jest.mock()
describe('Overview Test', () => {
// Mock the module and its functions
jest.mock('./someFile', () => ({
__esModule: true,
someFunction: jest.fn(() => 'Mocked someFunction!')
}));
// Import the function from the mocked module
const { someFunction } = require('./someFile');
test('snapshot', () => {
// Execute the mocked function
const someResult = someFunction();
// Expect to return the mocked value
expect(someResult).toBe('Mocked someFunction!');
});
});
You have to import the mocked modules after the jest.mock module mocking. You can create a jest.setup.js and configure it using setupFilesAfterEnv that can have your mocks inside it and then just import the modules like normal at the top of the test files.