esmock
/
1.9.6
esmock 1.9.6
Install from the command line:
Learn more about npm packages
$ npm install @iambumblehead/esmock@1.9.6
Install via package.json:
"@iambumblehead/esmock": "1.9.6"
About this version
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esmock provides native ESM import mocking for unit tests. Use examples below as a quick-start guide, see the descriptive and friendly esmock guide here, or browse esmock's test runner examples.
esmock is used with node's --loader
{
"name": "give-esmock-a-star",
"type": "module",
"scripts": {
"test": "node --loader=esmock --test",
"test-mocha": "mocha --loader=esmock",
"test-tap": "NODE_OPTIONS=--loader=esmock tap",
"test-ava": "NODE_OPTIONS=--loader=esmock ava",
"test-uvu": "NODE_OPTIONS=--loader=esmock uvu spec",
"test-tsm": "node --loader=tsm --loader=esmock --test *ts",
"test-ts-node": "node --loader=ts-node/esm --loader=esmock --test *ts",
"test-jest": "NODE_OPTIONS=--loader=esmock jest"
},
"jest": {
"runner": "jest-light-runner"
},
}esmock has the below signature
await esmock(
'./to/module.js', // path to target module being tested
{ ...childmocks }, // mock definitions imported by target module
{ ...globalmocks }) // mock definitions imported everywhereesmock examples
import test from 'node:test'
import assert from 'node:assert/strict'
import esmock from 'esmock'
test('should mock local files and packages', async () => {
const stringy = await esmock('../src/stringy.js', {
stringifierpackage: JSON.stringify,
'#icons': { kasa: '☂' },
'../src/hello.js': {
default: () => 'world',
exportedFunction: () => ({ icon: 'kasa' })
}
})
assert.strictEqual(stringy(), JSON.stringify({ kasa: 'world ☂' }))
})
test('should do global instance mocks —third param', async () => {
const { getFile } = await esmock('../src/main.js', {}, {
fs: {
readFileSync: () => 'returns this globally'
}
})
assert.strictEqual(getFile(), 'returns this globally')
})
test('should mock "await import()" using esmock.p', async () => {
// using esmock.p, mock definitions are kept in cache
const doAwaitImport = await esmock.p('../awaitImportLint.js', {
eslint: { ESLint: cfg => cfg }
})
// mock definition is returned from cache, when import is called
assert.strictEqual(await doAwaitImport('cfg'), 'cfg')
// a bit more info are found in the descriptive guide
})
// a "partial mock" merges the new and original definitions
test('should suppport partial mocks', async () => {
const pathWrap = await esmock('../src/pathWrap.js', {
path: { dirname: () => '/path/to/file' }
})
// an error, because path.basename was not defined
await assert.rejects(async () => pathWrap.basename('/dog.png'), {
name: 'TypeError',
message: 'path.basename is not a function'
})
// use esmock.px to create a "partial mock"
const pathWrapPartial = await esmock.px('../src/pathWrap.js', {
path: { dirname: () => '/home/' }
})
// no error, because "core" path.basename was merged into the mock
assert.deepEqual(pathWrapPartial.basename('/dog.png'), 'dog.png')
assert.deepEqual(pathWrapPartial.dirname(), '/home/')
})