How to generate a coverage report with vscode extension tests - testing

Question

I'm implementing a VSCode extension. I set up the project following this link.
It generates a starter project with a src/test/runTest.ts file:
import * as path from 'path';
import { runTests } from '#vscode/test-electron';
async function main() {
try {
// The folder containing the Extension Manifest package.json
// Passed to `--extensionDevelopmentPath`
const extensionDevelopmentPath = path.resolve(__dirname, '../../');
// The path to test runner
// Passed to --extensionTestsPath
const extensionTestsPath = path.resolve(__dirname, './suite/index');
// Download VS Code, unzip it and run the integration test
await runTests({ extensionDevelopmentPath, extensionTestsPath });
} catch (err) {
console.error('Failed to run tests');
process.exit(1);
}
}
main();
And a command in the package.json:
{
"compile": "tsc -p ./",
"pretest": "npm run compile && npm run lint",
"lint": "eslint src --ext ts",
"test": "node ./out/test/runTest.js"
}
Is there a way to generate a coverage report with it?

Answer 1

VSCode extension unittesting uses Mocha under the hood. You can generate coverage reports like in any other Typescript/Javascript project using one of the many available frameworks, e.g. c8, jest, istanbul, etc.
Install the framework of your choice, here I use c8
npm i --save-dev c8
and add to scripts
"scripts": {
"compile": "tsc -p ./",
"pretest": "npm run compile && npm run lint",
"lint": "eslint src --ext ts",
"test": "node ./out/test/runTest.js",
"coverage": "c8 --check-coverage npm run test"
}
Depending on your extension you might need to create a configuration file with the files you want to check for coverage. Here we are checking the compiled .js files placed under the out/ dir and we also excluding the files responsible for unittesting i.e. out/test/ (usually).
.c8rc
{
"all": true,
"include": ["out/**"],
"exclude": ["**/node_modules/**", "out/test/"],
"reporter": ["html", "text"]
}
Run the coverage script and you should get an output of your coverage
npm run coverage