ESM module mocking via Node loader
Let's mock some ESM modules. This has ZERO OVERHEAD when the loader is not in use. This was last tested on Node 16.14 but uses an experimental API that does in fact change (actually - I've had it change on me over a few months).
import * as zx from "zx";
import got from "got";
console.log(Object.keys(zx));
console.log(zx.fs.readFileSync('./package.json', 'utf8'));
console.log('Has custom method?',
'customMethod' in zx ? `Yes: ${zx.customMethod()}`: 'No');
(async () => {
console.log(await got('https://httpbin.org/json').json());
console.log(await got('https://httpbin.org/specialMockUrl').json()); // Will 404
})();Run normally, no loader:
~/esm-mock via v16.14.0
❯ node index.js
[
'$', 'ProcessOutput',
'ProcessPromise', 'YAML',
'argv', 'cd',
'chalk', 'fetch',
'fs', 'glob',
'globby', 'nothrow',
'os', 'path',
'question', 'quiet',
'registerGlobals', 'sleep'
]
{
"type": "module",
"dependencies": {
"esm": "^3.2.25",
"got": "^12.0.1",
"sinon": "^13.0.1",
"zx": "^5.2.0"
}
}
Has custom method? No
{
slideshow: {
author: 'Yours Truly',
date: 'date of publication',
slides: [ [Object], [Object] ],
title: 'Sample Slide Show'
}
}
node:internal/process/promises:265
triggerUncaughtException(err, true /* fromPromise */);
HTTPError: Response code 404 (NOT FOUND)
...
Run with loader, to install mocks:
~/esm-mock via v16.14.0
❯ node --no-warnings --experimental-loader=./loader.mjs index.js
MATCHED specifier=zx source=/hames/esm-mock/index.js mock=node_modules/zx/index.mjs
MATCHED specifier=got source=/hames/esm-mock/index.js mock=/hames/esm-mock/node_modules/got/dist/source/index.js
[
'$', 'ProcessOutput',
'ProcessPromise', 'YAML',
'argv', 'cd',
'chalk', 'customMethod',
'fetch', 'fs',
'glob', 'globby',
'nothrow', 'os',
'path', 'question',
'quiet', 'registerGlobals',
'sleep'
]
mockmock
Has custom method? Yes: 200
NETWORK REQ: https://httpbin.org/json
{
slideshow: {
author: 'Yours Truly',
date: 'date of publication',
slides: [ [Object], [Object] ],
title: 'Sample Slide Show'
}
}
MOCK NETWORK REQ: https://httpbin.org/specialMockUrl
{ "mock": "mockmockmock" }
The mocks are in the loader for now. They could be anywhere. It's all just
vanilla JS. No frameworks. No magic. You'd probably want to fs.readFileSync it
instead of hardcoding it in like I did.
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