esmock
/
2.0.8
esmock 2.0.8
Install from the command line:
Learn more about npm packages
$ npm install @iambumblehead/esmock@2.0.8
Install via package.json:
"@iambumblehead/esmock": "2.0.8"
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 --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 packages and local files', async () => {
const cookup = await esmock('../src/cookup.js', {
addpkg: (a, b) => a + b,
'#icon': { coffee: '☕', bacon: '🥓' },
'../src/breakfast.js': {
default: () => ['coffee', 'bacon'],
addSalt: meal => meal + '🧂'
}
})
assert.strictEqual(cookup('breakfast'), '☕🥓🧂')
})
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 wiki guide
})
test('should support "strict" mocking, at esmock.strict', async () => {
// replace original module definitions and do not merge them
const pathWrapper = await esmock.strict('../src/pathWrapper.js', {
path: { dirname: () => '/path/to/file' }
})
// error, because "path" mock above does not define path.basename
await assert.rejects(async () => pathWrapper.basename('/dog.png'), {
name: 'TypeError',
message: 'path.basename is not a function'
})
})