Is it possible to mock a binary's imports? about esmock

[tommy-mitchell]

Seems like it's possible using testdouble / quibble:

// src/helpers.js
export const foo = () => "foo";

// src/cli.js
import { foo } from "./helpers.js";

console.log(foo());
//=> expected: "foo"

// test.js
import * as td from "test-double";

await td.replaceEsm("./src/helpers.js", { foo: () => "bar" });

await import("./src/cli.js");
//=> actual: "bar"

[koshic]

@tommy-mitchell may be I missed something, but why you can't use globalmocks from

await esmock(
  './to/module.js', // filepath to the source module being tested
  import.meta.url, // parentUrl from which mocked modules should be resolved
  { ...childmocks }, // mock definitions imported by the source module, directly
  { ...globalmocks }) // mock definitions imported anywhere in the source import tree

[iambumblehead]

If I try running the first code snippet, the CLI is invoked without any mocks being applied.

Maybe the path should be "../src/helpers.js"?

await esmock("../src/cli.js", {
- "./helpers.js": {
+ "../src/helpers.js": {
    foo: someSpyOrStub(),
    bar: someSpyOrStub(),
  },
});

esmock should throw an error if no module is found at the "helpers.js" path. We can only guess about the layout and naming of your files

[iambumblehead]

though I don't know what your cli file looks like and maybe the idea is not helpful, perhaps the cli file could be made into a basic wrapper file that imports and calls more typical javascript file. The typical javascript file could be mocked more easily as a target for unit-tests eg,

app.cli.js

#! /usr/bin/env node
import app from './app.mjs';

(async () => {
  try {
    const res = await app( process.env );

    console.log('[...] cli success!:', JSON.stringify(res, null, '  '));
  } catch (e) {
    console.error(`Error!!: ${e.message}`);

    throw new Error('cli failed!');
  }
})();

Using a cli file like this one, the regular "app" could be unit-tested in a typical sort of way where env vars would become params the app is called with

[iambumblehead]

@tommy-mitchell I could be misunderstanding something but agree with @koshic that this form should work for your case

await esmock("../src/cli.js", {
  "../src/helpers.js": {
    foo: someSpyOrStub(),
    bar: someSpyOrStub()
  }
});

[tommy-mitchell]

My issue was an incorrect module specifier and some confusion about how a module gets invoked. Besides the issue in #215, this is working as intended.