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--experimental-test-module-mocks is not working as expected #55891
Description
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
Reacted by Fil Maj
Reacted by Tkinfolks
Activity
cjihrig commentedon Nov 17, 2024
Is axios actually installed, or are you trying to mock a module that does not exist?
0hmX commentedon Nov 18, 2024
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 commentedon Nov 18, 2024
Maybe we should add a comment regarding that in the documentation (assuming there isn't one already)
cjihrig commentedon Nov 18, 2024
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.
alltom commentedon Jul 2, 2025
This just bit me. :) Two things:
pmarchini commentedon Jul 2, 2025
I think we should support this use case.
Specifically, I also believe that adding a parameter to throw an exception when mocking a non-existent dependency could be very useful.
Personally, I think it should be the default behaviour, but it would introduce a breaking change that shouldn't be underestimated.
alltom commentedon Jul 18, 2025
In case it helps others:
I've been working around this by creating a module named obsidianWrapper that simply contains
export * from 'obsidian';, importing that everywhere instead of 'obsidian' proper, and mocking obsidianWrapper in tests instead.filmaj commentedon Sep 4, 2025
I also think mocking non-existent modules should be supported. My use case: I work for a company that provides a function-as-a-service feature. Our company maintains a "function wrapper" that
imports userland code. In tests of this function wrapper, I would like to mock the userland code being imported - even if it doesn't exist.github-actions commentedon Apr 26, 2026
This issue has been marked as stale due to 210 days of inactivity.
It will be automatically closed in 30 days if no further activity occurs. If this is still relevant, please leave a comment or update it to keep it open.
filmaj commentedon Apr 26, 2026
Please do not mark this as stale 😄 🙏
github-actions commentedon Jul 27, 2026
This issue has been marked as stale due to 90 days of inactivity.
It will be automatically closed in 30 days if no further activity occurs. If this is still relevant, please leave a comment or update it to keep it open.
filmaj commentedon Jul 28, 2026
Not stale dearest GitHub Robot 🙏
test_runner: support mocking non-existent modules
github-actions commentedon Oct 28, 2026
This issue has been marked as stale due to 90 days of inactivity.
It will be automatically closed in 30 days if no further activity occurs. If this is still relevant, please leave a comment or update it to keep it open.
alltom commentedon Oct 28, 2026
I still think about this every time I have to import
"obsidianWrapper"instead of"obsidian".