Testing Node.js with Jasmine

Async Testing

var asyncWork = function(callback) {
  setTimeout(callback, 200);
};

describe('async', function(){
  it('test', function(){
    var called = false;
    asyncWork(function() {
      called = true;
    });

    waitsFor(function(){ return called; });

    runs(function(){
      expect(called).toBeTruthy();
    });
  });
});

Simple Mocking

var read = function() {
  var stdin = process.openStdin();

  stdin.on('data', function (data) {
    console.log(data);
  });
};

Simple Mocking

describe('stdin', function(){
  it('test', function(){
    var ev = new events.EventEmitter();
    process.openStdin = function () { return ev; };

    var result = null;
    console.log = function(msg) {
      result = msg;
    };

    read();
    ev.emit('data', 'something');

    waitsFor(function(){ return result; });
    runs(function(){
      expect(result).toEqual('something');
}); }); });

Spies

var module = {
  actOne: function(){
    this.actTwo();
  },
  actTwo: function(){
    console.log('act two!');
  }
};

describe("spies test", function(){
  it("can spy", function(){
    spyOn(module, 'actTwo')
    module.actOne();
    expect(module.actTwo).toHaveBeenCalled();
  });
});

Spies

var asyncWork= function(callback){
  callback();
};

describe("spies test", function(){
  it("can spy", function(){
    var spy = jasmine.createSpy();
    asyncWork(spy);
    expect(spy).toHaveBeenCalled();
  });
});

Avoiding Test Pollution

describe('test pollution', function(){
  it('pollute tests', function(){
    process.openStdin = function () { return 1; };
    //test stuff
  });

  it('polluted test', function(){
    expect(function(){
      //process.openStdin is still mocked here!
      process.openStdin().on('data', function(data) {
        //process data
      });
    }).toThrow(new Error("Object 1 has no method 'on'"));
  });
});

Avoiding Test Pollution

describe('fixed test pollution', function(){
  beforeEach(function(){
    this._openStdin = process.openStdin;
  });

  afterEach(function(){
   process.openStdin = this._openStdin;
  });

  var mockedOpenStdin = function(){ return 1; };

  it('no longer pollute tests', function(){
    process.openStdin = mockedOpenStdin;
  });

  it('no longer polluted test', function(){
    expect(process.openStdin).toNotEqual(mockedOpenStdin);
}); });

Mocking Dates

global.currentDate = function(){
  return new Date();
};

var fakeDate = function(year, month, day) {
  spyOn(global, "currentDate").andCallFake(function() { 
    return new Date(year, month, day);
  });
};

describe("date test", function(){
  it("can spy currentDate", function(){
    fakeDate(2001, 11, 11);

    var now = global.currentDate();
    expect(now.getFullYear()).toEqual(2001);
  });
});

Mocking Dates

describe("mocking Dates", function(){
  it("can mock global.Date", function(){
    this._Date = Date;
    var testContext = this;

    spyOn(global, 'Date').andCallFake(function(){
      return new testContext._Date(1999, 4, 8);
    });

    var raw = new Date();
    var old = new this._Date(1900, 10, 10);

    expect(raw.getFullYear()).not.toEqual(old.getFullYear());
  });
});

Matchers

Custom Matchers

var emitter = new events.EventEmitter();

describe("event emitter matcher", function(){
  beforeEach(function(){
    this.addMatchers({
      toHaveListener: function(event) {
        return this.actual.listeners(event).length > 0;
      }
    });
  });

  it("can test event emitter better with matchers", function(){
    emitter.on('data', function(){ console.log('data!'); });
    expect(emitter).toHaveListener('data');
  });
});

About

Sean Massa

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