aws-sdk-mock

AWSome mocks for Javascript aws-sdk services.

This module was created to help test AWS Lambda functions but can be used in any situation where the AWS SDK needs to be mocked.

If you are new to Amazon WebServices Lambda (or need a refresher), please checkout our our
Beginners Guide to AWS Lambda: https://github.com/dwyl/learn-aws-lambda

• Why
• What
• Getting Started
• Documentation
• Background Reading

Why?

Testing your code is essential everywhere you need reliability.

Using stubs means you can prevent a specific method from being called directly. In our case we want to prevent the actual AWS services to be called while testing functions that use the AWS SDK.

What?

Uses Sinon.js under the hood to mock the AWS SDK services and their associated methods.

How? (Usage)

install aws-sdk-mock from NPM

npm install aws-sdk-mock --save-dev

Use in your Tests

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

AWS.mock('DynamoDB', 'putItem', function (params, callback){
  callback(null, "successfully put item in database");
});

AWS.mock('SNS', 'publish', 'test-message');

/**
    TESTS
**/

AWS.restore('SNS', 'publish');
AWS.restore('DynamoDB');
// or AWS.restore(); this will restore all the methods and services

NB: The AWS Service needs to be initialised inside the function being tested in order for the SDK method to be mocked e.g for an AWS Lambda function example 1 will cause an error region not defined in config whereas in example 2 the sdk will be successfully mocked.

Example 1:

var AWS      = require('aws-sdk');
var sns      = AWS.SNS();
var dynamoDb = AWS.DynamoDB();

exports.handler = function(event, context) {
  // do something with the services e.g. sns.publish
}

Example 2:

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

exports.handler = function(event, context) {
  var sns      = AWS.SNS();
  var dynamoDb = AWS.DynamoDB();
  // do something with the services e.g. sns.publish
}

Don't worry about the constructor configuration

Some constructors of the aws-sdk will require you to pass through a configuration object.

var csd = new AWS.CloudSearchDomain({
  endpoint: 'your.end.point',
  region: 'eu-west'
});

Most mocking solutions with throw an InvalidEndpoint: AWS.CloudSearchDomain requires an explicit 'endpoint' configuration option when you try to mock this.

aws-sdk-mock will take care of this during mock creation so you won't get any configuration errors!
If configurations errors still occur it means you passed wrong configuration in your implementation.

Documentation

AWS.mock(service, method, replace)

Replaces a method on an AWS service with a replacement function or string.

AWS.restore(service, method)

Removes the mock to restore the specified AWS service

If AWS.restore is called without arguments (AWS.restore()) then all the services and their associated methods are restored i.e. equivalent to a 'restore all' function.

Background Reading

• Mocking using Sinon.js
• AWS Lambda

Contributions welcome! Please submit issues or PRs if you think of anything that needs updating/improving