How to stub aws-sdk
Let's say I have
// file sample.js
var aws = require('aws-sdk');
var dynamoDB = new aws.DynamoDB();
exports.processData = function(){
var data = dynamoDB.getItem(params);
// so something with data
};
How can I write unit tests for the above code example.
//file sample_test.js
var aws = require('aws-sdk');
var sinon = require('sinon');
// the following code doesnt seem to stub the function
// the actual function is still used in sample.js
var getItemStub = sinon.stub();
aws.DynamoDB.prototype.getItem = getItemStub;
var sample = require('./sample');
Which would be a good way to stub the aws-sdk api. I was thinking about using SinonJS to achieve it, but I am open to other libraries and suggestions.
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2 answers
My current solution is to expose the function in sample.js as shown below.
function overRide(data) {
dynamoDB = data.dynamoDB;
}
if(process.env.NODE_ENV === 'test') {
exports.overRide = overRide;
}
Now in my test case I can do the following which will close the aws api.
//file sample_test.js
var aws = require('aws-sdk');
var sinon = require('sinon');
var sample = require('./sample');
var ddb = new aws.DynamoDB();
ddb.getItem = sinon.stub();
sample.overRideAWS({dynamoDB: ddb});
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We've created the aws-sdk-mock npm module that mocks all AWS SDK services and methods. https://github.com/dwyl/aws-sdk-mock
It is very easy to use. Just call AWS.mock with service, method and stub function.
AWS.mock('DynamoDB', 'getItem', function(params, callback) {
callback(null, 'success');
});
Then restore the methods after testing by calling:
AWS.restore('DynamoDB', 'getItem');
Or to restore all calls:
AWS.restore();
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