JavaScript unit testing in under 30 lines

tester.js

const PASS = ['32'];  // green
const FAIL = ['31', '1'];  // red, bold

function logStyle(ansiEscapeCodes, text) {
  console.log(`\x1b[${ansiEscapeCodes.join(';')}m${text}\x1b[0m`);
}

class Tester {
  constructor() {}

  test(name, fn) {
    try {
      fn.bind(this)();
      logStyle(PASS, `${name} PASSED`);
    }
    catch (e) {
      logStyle(FAIL, `${name} FAILED:
  ${e}`);
      process.on('exit', () => (process.exitCode = 1));
    }
  }

  assertEquals(arg1, arg2) {
    if (arg1 != arg2) throw new Error(`Expected ${arg1} to equal ${arg2}`);
  }
  
  assert(condition) {
    if (!condition) throw new Error(`Expected ${condition} to be truthy`);
  }
}


/*
Usage:

  const t = new Tester();

  t.test('testName', () => {
    t.assertEquals('dog'.length, 3);  // will pass
  });

  t.test('anotherTestName', () => {
    t.assert(false);  // will fail
  });

*/