I am authoring a unit test to test a function in a VSCode extension. I need to mock another function that my code under test depends on. However, the mocha test runner fails with Error: Cannot find module 'vscode'.

The VSCode docs explain how to run integration tests with the full VS Code emulator, but I don't want to do this. I only want to run unit tests without the emulator. However, it seems like the vscode dependency does not get imported into tests without the emulator.

I've tried npm install vscode --save-dev but that hasn't helped.

Here is my test:

// getGhciBasePath.spec.ts

import { getGhciBasePath } from './getGhciBasePath';
import { assert } from 'chai';
import * as sinon from 'sinon';
import * as config from './config';
import * as os from 'os';

describe('getGhciBasePath', () => {

    it('should load .ghcup path if no path is configured', () => {
        sinon.stub(config, 'ghciPath').returns('');
        sinon.stub(os, 'homedir').returns('/Users/hank');
        const actual = getGhciBasePath();
        assert.equal('/Users/hank/.ghcup/bin', actual);
    });
});

And the code under test:

// getGhciBasePath.ts

import * as os from 'os';
import * as path from 'path';
import * as config from './config';

export const getGhciBasePath = () => {
    const configuredPath = config.ghciPath();

    if (configuredPath && configuredPath.trim().length > 0) {
        return configuredPath;
    }

    return path.join(os.homedir(), '.ghcup', 'bin');
};

And finally the config file dependency:

// config.ts
import * as vscode from 'vscode';

const getConfiguration = vscode.workspace.getConfiguration;

export const ghciPath = () => {
    return vscode.workspace
        .getConfiguration('foo').get('ghciPath', 'ghci');
}

My npm script:

"test": "mocha --require tsx src/*.spec.ts"

I'm trying to stub the config.ghciPath() call so that the vscode library isn't invoked during the test. But yet, sinon can't seem to mock the function to prevent it from being imported.

Thoughts?