CODEWITHSUNDEEP
javascriptsinonstubbing
John Smith
John Smith

Reputation: 6259

Stub a Function with Callback

Normally I use this code: 

  aws_stub.S3 = function(){};
  var fake_aws_listObjects = function(params, func){func("failure", null)};
  var fake_aws_listObjects_stub = sinon.spy(fake_aws_listObjects);
  aws_stub.S3.prototype.listObjects = fake_aws_listObjects_stub;

To stub a function like the following one:

new AWS.S3().listObjects(that.build_params(), function(err, data) {
  if(err){
    that.make_failure_callback();
  }
  else{
    that.add_keys(data);

    if(data.IsTruncated){
      that.make_request(data.NextMarker);
    }else{
      that.make_success_callback(that.keys);
    }
  }
});

The problem with this stubbing is that on each request it returns the same

Now I wanted to do is different stubbing for each call:

  aws_stub.S3 = function(){};
  var fake_aws_truncated = function(params, func){func(null, {
    Contents: [{Key: "3fb252ba-0724-438c-93b6-8cd0fd972a8e/image/1:::2.jpg"}],
    IsTruncated: true,
    NextMarker: "nextMarker"
    })};
  var fake_aws_listObjects = function(params, func){func(null, {Contents: [{
    Key: "3fb252ba-0724-438c-93b6-8cd0fd972a8e/image/2:::3.jpg"
  }]})};

  var fake_aws_listObjects_stub = sinon.stub();
     fake_aws_listObjects_stub.onCall(0).returns(fake_aws_truncated);
      fake_aws_listObjects_stub.onCall(1).returns(fake_aws_listObjects);

  aws_stub.S3.prototype.listObjects = fake_aws_listObjects_stub;

The problem seems to be returns, it doesn't execute the function!!

I also cannot write it like this:

fake_aws_listObjects_stub.onCall(0) = fake_aws_truncated;

Because this would be a wrong hand assignment!

What do I have to change? Here are the sinon docs: http://sinonjs.org/docs/

Thanks!!

Upvotes: 0

Views: 645

Answers (1)

robertklep
robertklep

Reputation: 203231

I would probably go about it another way.

If you want to stub AWS.S3.prototype.listObjects, I would do that like so:

var stub = sinon.stub(AWS.S3.prototype, 'listObjects');

To call the callback with various values, use stub.yields():

stub.onCall(0).yields(null, {
  Contents    : [{Key: "3fb252ba-0724-438c-93b6-8cd0fd972a8e/image/1:::2.jpg"}],
  IsTruncated : true,
  NextMarker  : "nextMarker"
});

stub.onCall(1).yields(null, {
  Contents : [{Key: "3fb252ba-0724-438c-93b6-8cd0fd972a8e/image/2:::3.jpg"}]
});

To test your code, you just call listObjects like before:

var s3 = new AWS.S3();
s3.listObjects(params, function(err, value) {
  ...`value` is now one of the fixtures you declared above...
});

To restore to the original version of the method, use one of these:

stub.restore();
// OR:
AWS.S3.prototype.listObjects.restore();

Upvotes: 3

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