Run ts-mocha programmatically (in a script)

test-with-ts-mocha.js

require('ts-mocha');
const Mocha = require('mocha');
const fs = require('fs');

let testSubject = null;
if (process.argv.length === 3) {
    testSubject = process.argv[2];
}

const mocha = new Mocha({ timeout: 50000 });
if (testSubject && testSubject.endsWith('.test.ts')) {
    mocha.addFile(`tests/${testSubject}`);
    console.log(`using single file ${testSubject}`);
} else if (testSubject) {
    // expect test subject to be a folder
    fs.readdirSync(`tests/${testSubject}`)
        .filter(file => file.endsWith('.test.ts'))
        .forEach(file => mocha.addFile(`tests/${testSubject}/${file}`));
} else {
    fs.readdirSync('tests/units')
        .filter(file => file.endsWith('.test.ts'))
        .forEach(file => mocha.addFile(`tests/${file}`));
}

mocha.run((failures) => {
    process.on('exit', () => {
        process.exit(failures); // exit with non-zero status if there were failures
    });
    // Explicitly kill application, something makes it hang.
    process.exit(failures);
});