Asynchronous test runner

runner.js

module.exports = Runner;

function Runner() {
  this.stack = [];
  this.passed = 0;
  this.failed = 0;
}

Runner.prototype.it = function (msg, test) {
  this.stack.push(new Test(msg, test));
};

Runner.prototype.run = function () {

  this.test = this.stack.shift();

  if (!this.test) {
    var exitCode = this.failed.length ? 1 : 0;
    this.summary();
    process.exit(exitCode);
  };

  console.log(this.test.msg);

  var self = this;
  this.test.func(function () {
    self.report();
    self.run.bind(self)();
  });
};

Runner.prototype.summary = function () {
  console.log('Passed: ' + this.passed +
    ' Failed: ' + this.failed);
};

Runner.prototype.report = function () {
  if (this.test.passed) {
    console.log('\tPASSED');
    this.passed++;
  } else {
    console.log('\tFAILED');
    this.failed++;
  }
};

Runner.prototype.fail = function () {
  this.test.fail();
};

function Test(msg, func) {
  this.msg = msg;
  this.func = func;
  this.passed = true;
}

Test.prototype.fail = function () {
  this.passed = false;
};

test.js

var TestRunner = require('./runner.js'),
  test = new TestRunner();

test.it('Should do something that takes a second', function (next) {
  setTimeout(next, 1000);
});

test.it('Should do something else', function (next) {
  next();
});

test.it('Should try to do something and fail', function (next) {
  test.fail();
  next();
});

test.run();

Should do something that takes a second
    PASSED
Should do something else
    PASSED
Should try to do something and fail
    FAILED
Passed: 2 Failed: 1