mock-aws

Easily mock aws-sdk API methods to enable easier testing of applications which use the AWS SDK for JavaScript.

Under the hood, this stubs aws-sdk methods using sinon.js.

API

• AWS.mock(service, method, data)
• AWS.restore(service, method)
• AWS.restore(service)
• AWS.restore()

AWS.mock(service, method, data)

Mocks an AWS service method to return the specified test data or a function

Arguments

• service (string): the name of the AWS service that the method belongs to e.g. EC2, Route53 etc.
• method (string): the service's method to be be mocked e.g. describeTags
• data (object): the test data that the mocked method should return or a function that is called

The parameter data can be either fixed data, in which case the original callback will be called with that data, or it can be a function. If it is a function, then when the mocked service is called, your function will be called.
If it is a function, it will be passed all of the parameters passed to the original AWS SDK call, including the callback. You are expected to call the callback.
Example of fixed data:

var AWS = require('mock-aws');
var ec2 = new AWS.EC2();

AWS.mock('EC2', 'describeTags', [ 'one', 'two', 'three' ]);
ec2.describeTags({}, function(err, data) {
  console.log(data); // data should equal [ 'one', 'two', 'three' ];
});

Example of function:

var AWS = require('mock-aws');
var ec2 = new AWS.EC2();

AWS.mock('EC2', 'describeTags', function(params,callback){
  params = params || {};
  if (params.special) {
    callback(null,"special");
  } else if (params.strange) {
    callback(null,"weird");
  } else {
    callback("ERROR!");
  }
});
ec2.describeTags({}, function(err, data) {
  console.log(err);  // err should equal "ERROR!"
  console.log(data); // data should be undefined
});
ec2.describeTags({special: true}, function(err, data) {
  console.log(err);  // err should be null
  console.log(data); // data should be "special"
});
ec2.describeTags({strange:true}, function(err, data) {
  console.log(err);  // err should be null
  console.log(data); // data should be "weird"
});

AWS.restore(service, method)

Removes mocked service method to restore the original functionality

Arguments

• service (string): the name of the AWS service that the method belongs to e.g. EC2, Route53 etc.
• method (string): the service's method to be be restored e.g. describeTags

var AWS = require('mock-aws');

// Mock some EC2 methods to return specified test data
AWS.mock('EC2', 'describeTags', [ 'one', 'two', 'three' ]);
var ec2 = new AWS.EC2();

// EC2 methods should return specified test data
ec2.describeTags({}, function(err, data) {
  console.log(data); // data should equal [ 'one', 'two', 'three' ];
});

// Call restore with a service & method
AWS.restore('EC2', 'describeTags');

// describeTags method now returns real AWS data
ec2.describeTags({}, function(err, data) {
  console.log(data); // data should equal real data from AWS
});

AWS.restore(service)

Removes ALL mocked methods for given service to restore the original functionality

Arguments

• service: (string) the name of the AWS service to restore e.g. EC2, Route53 etc.

var AWS = require('mock-aws');
var ec2 = new AWS.EC2();

AWS.mock('EC2', 'describeTags', [ 'one', 'two', 'three' ]);
AWS.mock('EC2', 'describeVpcs', 'vpcs');
ec2.describeTags({}, function(err, data) {
  console.log(data); // data should equal [ 'one', 'two', 'three' ];
});
ec2.describeVpcs({}, function(err, data) {
  console.log(data); // data should equal 'vpcs';
});

AWS.restore('EC2');
ec2.describeTags({}, function(err, data) {
  console.log(data); // data should be real data from AWS
});
ec2.describeVpcs({}, function(err, data) {
  console.log(data); // data should be real data from AWS
});

AWS.restore()

Removes ALL mocked services & methods to restore the original functionality

var AWS = require('mock-aws');

var ec2 = new AWS.EC2();
var s3 = new AWS.S3();

AWS.mock('EC2', 'describeTags', [ 'one', 'two', 'three' ]);
AWS.mock('EC2', 'describeVpcs', 'vpcs');

AWS.mock('S3', 'listBuckets', { buckets: [] });

ec2.describeTags({}, function(err, data) {
  console.log(data); // data should equal [ 'one', 'two', 'three' ];
});
ec2.describeVpcs({}, function(err, data) {
  console.log(data); // data should equal 'vpcs';
});

s3.listBuckets({}, function(err, data) {
  console.log(data); // data should equal { buckets: [] };
})


AWS.restore('EC2');
ec2.describeTags({}, function(err, data) {
  console.log(data); // data should be real data from AWS
});
ec2.describeVpcs({}, function(err, data) {
  console.log(data); // data should be real data from AWS
});
s3.listBuckets({}, function(err, data) {
  console.log(data); // data should equal { buckets: [] };
})

Example

I want to build and test a tag validator that returns the id's of any EBS volumes which don't have a tag called 'name'. My production code for my tag-validator may look something like the following:

var AWS = require('aws-sdk');

function getNamelessVolumes(region, callback) {

  var ec2 = new AWS.EC2({ region: region });

  ec2.describeVolumes({}, function(err, data) {
    if (err) callback(err, null);
    var namelessVolumes = [];
    data.Volumes.forEach(function(volume) {
      var named = false;
      for (var i = 0; i < volume.Tags.length; i++) {
        if (volume.Tags[i].Key.toLowerCase() === 'name') {
          named = true;
          break;
        }
      }
      if (!named) {
        namelessVolumes.push(volume.VolumeId);
      }
    });
    callback(null, namelessVolumes);
  });

}

module.exports = {
  getNamelessVolumes: getNamelessVolumes
};

In order to test my validator, I don't want to actually call AWS, nor do I want to have to change my production code. The mock-aws module solves this problem - I can easily mock the describeVolumes method in my test then call the tag validator as normal. This way I can use varying test data to fully test the getNamelessVolumes function, without relying on AWS services. First I setup my test data:

{
  "Volumes": [
    {
      "VolumeId": "v-111",
      "Tags": [
        {
          "Key": "name",
          "Value": "volume 1"
        },
        {
          "Key": "role",
          "Value": "test"
        }
      ]
    },
    {
      "VolumeId": "v-222",
      "Tags": [
        {
          "Key": "role",
          "Value": "test"
        }
      ]
    }
  ]
}

Now I can write my test, mocking describeVolumes() to return my test data

var should = require('should');
var AWS = require('mock-aws'); // include mock-aws instead of aws-sdk
var tagValidator = require('../lib/tag-validator');

describe('tag-validator', function() {
  describe('getNamelessVolumes()', function() {
    it('should return the ids of volumes which do NOT contain a "name" tag', function(done) {

      // Test data for the AWS method to return
      var testData = require('./test-data.json');

      // Mock the aws-sdk method 'describeVolumes' to return the test data
      AWS.mock('EC2', 'describeVolumes', testData);

      // Call the function I'm trying to test
      tagValidator.getNamelessVolumes('us-east-1', function(err, data) {
        // Assert that getNamelessVolumes() returned the correct results
        data.length.should.eql(1);
        data[0].should.eql('v-222');
        done();
      });

    });
  });
});

The point here is that I can test the functionality of my tag-validator without making real calls to AWS and I never had to modify my production code in order to make it testable. mock-aws handled it for me.
I built this for myself but feel free to use, share, submit bugs / pull requests, suggest changes or features etc.