describe.js

function Describe(title, testFunc, parent) {
  this._title = title;
  this._parent = parent;
  this._testFunc = testFunc;

  if ( ! this._parent ) { // root
    this.run();
  }
}

Describe.prototype.title = function() {
  var title = '';
  if ( this._parent ) {
    title = this._parent.title() + ' ' + this._title;
  } else {
    title = this._title;
  }
  return title;
};
Describe.prototype.setup = function(cb) {
  this._setup = cb;
};
Describe.prototype.teardown = function(cb) {
  this._teardown = cb;
};
Describe.prototype._describe = function(title, testFunc, verbose) {
  var describe = new Describe(title, testFunc, this);

  describe.setup(this._setup);
  describe.teardown(this._teardown);

  if ( this._setup ) {
    this._setup.call(describe);
  }
  describe.run(verbose);
  if ( this._teardown ) {
    this._teardown.call(describe);
  }
};
Describe.prototype.it = function(title, testFunc) {
  this._describe(title, testFunc, true);
};
Describe.prototype.describe = function(title, testFunc) {
  this._describe(title, testFunc, false);
};

Describe.prototype.run = function(verbose) {
  try {
    this._testFunc.call(this);
    if ( verbose ) {
      console.log('"' + this.title() + ' : Pass"\n');
    }
  } catch(e) {
    if ( verbose ) {
      console.log('"' + this.title() + ' : Fail"');
      console.log(e.message + "\n");
    }
  }
};

module.exports = function(title, testFunc) {
  return new Describe(title, testFunc);
};

describe_example.js

var assert = require('assert');
var describe = require('./describe');

function UriBuilder(baseUri) {
  var self = this;
  this.params = {};
  if ( baseUri.indexOf('?') >= 0 ) {
    var params = baseUri.match(/\?(.*)/);
    params[1].split('&').forEach(function(p) {
      var key_val = p.split('=');
      var key = key_val[0], val = key_val[1];
      self.params[key] = val;
    });
    this.baseUri = baseUri.substring(0, baseUri.indexOf('?'));
  } else {
    this.baseUri = baseUri;
  }
}

UriBuilder.prototype.build = function() {
  var params = this.params;
  var paramsArray = [];
  for (key in params) {
    paramsArray.push(key + '=' + encodeURIComponent(params[key]));
  }
  if( paramsArray.length > 0 ) {
    return this.baseUri + '?' + paramsArray.join('&');
  } else {
    return this.baseUri;
  }
};

describe('UriBuilder without initial params', function() {
  this.setup(function() {
    this.builder = new UriBuilder('http://www.codewars.com');
  });

  this.it('should build correct uri with set parameters', function(test) {
    this.builder.params.page = 1;
    this.builder.params.language = 'javascript';
    assert.equal(this.builder.build(), 'http://www.codewars.com?page=1&language=javascript');
  });
});

describe('UriBuilder with pre-existing params', function(){
  this.setup(function() {
    this.builder = new UriBuilder('http://www.codewars.com?page=1');
  });

  this.describe('should build correct uri', function() {
    this.it('without changes', function() {
      assert.equal(this.builder.build(), 'http://www.codewars.com?page=1');
    });

    this.describe('after', function() {
      this.it('updating params', function() {
        this.builder.params.page = 2;
        assert.equal(this.builder.build(), 'http://www.codewars.com?page=2');
      });

      this.it('deleting a param', function() {
        delete this.builder.params.page;
        assert.equal(this.builder.build(), 'http://www.codewars.com');
      });

      this.it('adding param again', function() {
        this.builder.params.page = 1;
        assert.equal(this.builder.build(), 'http://www.codewars.com?page=1');
      });
    });
  });
});