testdouble / testdouble/testdouble.js
Stubbing a CJS module from an ESM
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Description
Description
In the testdouble repo, I created examples/node-esm/test/lib/numbers-only-test.mjs with the following code.
import assert from 'assert'
import mocha from 'mocha'
import * as td from 'testdouble'
mocha.describe('numbers-only', function () {
mocha.it.only('goes boom', async function () {
const isNumber = td.replace('is-number');
const numbersOnly = await import('../../lib/numbers-only.mjs')
td.when(isNumber('a string')).thenReturn(true) // tee-hee, this is silly
const result = numbersOnly.default('a string')
assert.equal(result, true)
});
});
Based on what I read from the docs, I would expect this code to pass, but whenever ../../lib/numbers-only.mjs is loaded, the real is-number is resolved instead of the faked module.
Issue
the real module is being loaded instead of the fake.
Environment
-
node -v20.1.0 or 22.3.0: -
npm -v(oryarn --version) output: 10.5.2 or 10.8.1 -
npm ls testdouble(oryarn list testdouble) version: from the example
Failing Test
See above
Example Repo
See above
Runkit Notebook
- Create a Runkit notebook
- Invoke
var td = require('testdouble')at the top - Verify the behavior your issue is concerned with by clicking "Run"
- Link to the Runkit here
Code-fenced Examples
var td = require('testdouble')
// Your steps here.
Contributor guide
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First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start by running examples/node-esm/test/lib/numbers-only-test.mjs and trace td.replace('is-number') before ../../lib/numbers-only.mjs is dynamically imported. Check the ESM/CJS module-loading path involved in that example; done means the fake is-number module is used and the test assertion passes.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- javascript, node.js
- Domain
- devtools, testing-qa
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 32/100