--experimental-test-module-mocks is not working as expected

[cu8code]

Version

v24.0.0-pre

Platform

Linux fedora 6.11.6-200.fc40.x86_64 #1 SMP PREEMPT_DYNAMIC Fri Nov  1 16:09:34 UTC 2024 x86_64 GNU/Linux

Subsystem

No response

What steps will reproduce the bug?

This issue was observed inside the nodejs source code, when tying to create a benchmark
create a file benchmark/test_runner/mock-module.js

now copy this code

"use strict";

const { test } = require("node:test");

function main() {
  test(async (t) => {
    console.log("benchmark");

    try {
    // Create a mock module
    t.mock.module('axios', {
      namedExports: {
        get: (url) => url
      }
    });

    } catch (e) {
      console.error(e);
    }

    console.log("end");
  });
}

main()

now run this using ./node --experimental-test-module-mocks benchmark/test_runner/mock-module.js

You will get this output

benchmark
Error [ERR_MODULE_NOT_FOUND]: Cannot find package 'axios' imported from /home/ankan/Documents/git/me/node/benchmark/test_runner/mock-module.js
    at Object.getPackageJSONURL (node:internal/modules/package_json_reader:267:9)
    at packageResolve (node:internal/modules/esm/resolve:768:81)
    at moduleResolve (node:internal/modules/esm/resolve:854:18)
    at defaultResolve (node:internal/modules/esm/resolve:984:11)
    at nextResolve (node:internal/modules/esm/hooks:748:28)
    at resolve (node:internal/test_runner/mock/loader:78:35)
    at nextResolve (node:internal/modules/esm/hooks:748:28)
    at Hooks.resolve (node:internal/modules/esm/hooks:240:30)
    at handleMessage (node:internal/modules/esm/worker:199:24)
    at Immediate.checkForMessages (node:internal/modules/esm/worker:141:28) {
  code: 'ERR_MODULE_NOT_FOUND'
}
end
✔ <anonymous> (42.524333ms)
(node:91728) ExperimentalWarning: Module mocking is an experimental feature and might change at any time
(Use `node --trace-warnings ...` to show where the warning was created)
ℹ tests 1
ℹ suites 0
ℹ pass 1
ℹ fail 0
ℹ cancelled 0
ℹ skipped 0
ℹ todo 0
ℹ duration_ms 48.749785

As you can we we are trying to create a mock 'axios' module but we receive the error Cannot find package 'axios', which is unexpected as we are not even importing the module. The error is occurring because of the line t.mock.module

How often does it reproduce? Is there a required condition?

dose not need any special condition

What is the expected behavior? Why is that the expected behavior?

should create a mock module called axios

What do you see instead?

their is an error, saying package 'axios' not found, which is very unexpected

Additional information

No response

[cjihrig]

Is axios actually installed, or are you trying to mock a module that does not exist?

[cu8code]

I realize I made a bit of a mess earlier and completely overlooked an important detail: the package actually needs to be installed! Totally makes sense, but for some reason, I thought we could just create a random module and mock its implementation out of thin air. This issue should probably be closed, but I’ll leave that decision to the maintainers. Apologies to everyone for the incovinience!

[MoLow]

Maybe we should add a comment regarding that in the documentation (assuming there isn't one already)

[cjihrig]

We should also decide if we want to support mocking modules that do not exist. I don't think there is a technical reason we couldn't do it, but I don't know if that is something people actually want/need to do in the wild.