If you've encountered the issue of importing an entire module's contents under a namespace and the need to explicitly define each export by name, using ES modules provides no workaround.
In my opinion, the challenge arises from the mix of implicit behavior from 'vitest' and explicit behavior in your code. Personally, I find it easier to understand code when it is explicit. Consider this alternative approach to the 'vi.mock' method:
Let's assume the module you are testing is located at './src/example.ts'.
Mocking the Module
Create a mock module alongside your test module with the following structure:
Following the convention of '[name].test.mock.[ext]'
// ./src/example.test.mock.ts
import { createFsFromVolume, type IFs, Volume } from 'memfs';
// Mock factory to produce the simulated fs
export function createFs (): IFs {
const files = {
'./1.mp3': '1',
'./2.mp3': '2',
};
const dir = './musicFolder';
const volume = Volume.fromJSON(files, dir);
return createFsFromVolume(volume);
}
// Alternatively, directly export an instance if it's the only one needed
export const fs = createFs();
Testing Module
Adhering to the naming convention of '[name].test.[ext]'
Here are two ways to implement it:
First approach
// ./src/example.test.ts
import { expect, it } from 'vitest';
// If the actual `fs` from Node is required elsewhere in your test,
// maintain this import.
import * as fs from 'node:fs';
import { createFs } from './example.test.mock.js';
it('testing fs', async () => {
const fs = createFs();
const files = fs.readdirSync('./musicFolder');
expect(files).toBeTruthy();
});
// Utilize the real `fs` in other test scenarios...
Second approach
If the actual fs is not needed in your test, utilize the mocked version directly:
// ./src/example.test.ts
import { expect, it } from 'vitest';
import { fs } from './example.test.mock.js';
it('testing fs', async () => {
const files = fs.readdirSync('./musicFolder');
expect(files).toBeTruthy();
});
Conclusion
Both approaches to the test run smoothly without errors and pass successfully:
so-72860426 % node --version
v16.15.1
so-72860426 % npm run test
> <a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="295a46041e1b111f191d1b1f691907180719">[email protected]</a> test
> vitest
DEV v0.17.0 /stack-overflow/so-72860426
✓ src/example.test.ts (1)
Test Files 1 passed (1)
Tests 1 passed (1)
Time 906ms (in thread 34ms, 2666.13%)
PASS Waiting for file changes...
press h to show help, press q to quit
Here are the repository configuration files for replicating this setup:
./package.json:
{
"name": "so-72860426",
"version": "0.1.0",
"description": "",
"type": "module",
"scripts": {
"test": "vitest"
},
"keywords": [],
"author": "",
"license": "MIT",
"devDependencies": {
"@types/node": "^18.0.1",
"typescript": "^4.7.4",
"vitest": "^0.17.0"
},
"dependencies": {
"memfs": "^3.4.7"
}
}
./tsconfig.json:
{
"compilerOptions": {
"esModuleInterop": true,
"exactOptionalPropertyTypes": true,
"isolatedModules": true,
"lib": [
"esnext"
],
// "jsx": "react-jsx",
"module": "esnext",
"moduleResolution": "nodenext",
"noUncheckedIndexedAccess": true,
"strict": true,
"target": "esnext",
"useUnknownInCatchVariables": true
},
"include": [
"src/**/*"
]
}