Testing WorkerThreads with ts-mocha.

[akirilyuk]

Hi, when trying to create a test that tests the behavior of WorkerThreads, it fails to start the application with this error message, failing to parse my workerScript.ts:

import { parentPort } from "worker_threads";
^^^^^^

SyntaxError: Cannot use import statement outside a module

The application itself can be started with and is working via node -r ts-node/register/transpile-only

Is there any option to test WorkerThreads behaviour via ts-mocha at all?

[akirilyuk]

Until this issue is fixed, I have found a workaround so I am still able to test code which relies on WorkerThreads module:
Simply create a loader file as described below. You would then need to load the loader file via a Worker and this will then load the actual script and register ts-node if running in TS.

// this is a loader module to load the actual ts worker file
const path = require('path');
const {parentPort} = require("worker_threads");

try {
	const fileName = __filename.slice(__dirname.length + 1);
	const fileExtension = fileName.slice(fileName.length - 2);
    // only register ts-node if we are inside a .ts file
	if (fileExtension == "ts") {
		require('ts-node').register({
			project: __dirname.concat(process.env.NODE_ENV === "production" ? "../../../../tsconfig.production.json" : "../../../../tsconfig.json"),
			transpileOnly: true,
		});
	}
	require(path.resolve(__dirname, `./yourActualWorkerTask.${fileExtension}`));
} catch (error) {
	parentPort.postMessage({
		result: null,
		error
	});
}