Example of predictableNextTick

get-last-modified-fixed.js

var fs = require('fs');

var getLastModified = function(files, done) {
  var timestamps = new Array(files.length);
  var pending = files.length;

  files.forEach(function(file, idx) {
    fs.stat(file, function(err, stat) {
      timestamps[idx] = stat.mtime;

      if (!--pending) {
        done(null, timestamps);
      }
    });
  });
};

get-last-modified.js

var fs = require('fs');

var getLastModified = function(files, done) {
  var timestamps = [];

  files.forEach(function(file) {
    fs.stat(file, function(err, stat) {
      timestamps.push(stat.mtime);

      if (timestamps.length === files.length) {
        done(null, timestamps);
      }
    });
  });
};

get-last-modified.spec.js

// Jasmine Syntax
//
// Install npm dependencies first:
// npm install mocks
//
// Then, run unit test:
// jasmine-node .

describe('getLastModified', function() {

  var mocks = require('mocks');
  var mockery = {
    // reate a fake in-memory FS
    fs: mocks.fs.create({
      'one.js': mocks.fs.file('2012-01-01'),
      'two.js': mocks.fs.file('2012-02-02'),
      'three.js': mocks.fs.file('2012-02-02')
    })
  };

  // load the module (using fake FS)
  var getLastModified = mocks.loadFile('get-last-modified-fixed.js', mockery).getLastModified;


  it('should return last modified timestamps for every file', function() {
    var spy = jasmine.createSpy('done').andCallFake(function(err, timestamps) {
      expect(timestamps).toEqual([
        new Date('2012-01-01'), new Date('2012-02-02'), new Date('2012-02-02')
        ]);
    });

    mocks.predictableNextTick.pattern = [1, 0];
    getLastModified(['/one.js', '/two.js', '/three.js'], spy);

    // wait for done callback
    waitsFor(function() {return spy.callCount;});
  });
});