stubbing AWS Dynamodb documentClient for integration test - node.js

Question

im having some issues stubbing this dependency. I know there ir a aws-sdk-mock modules but mi goal its to stub it with sinon and chai.
Here is mi code,
Test code
const chai = require('chai');
const sinon = require('sinon');
const chaiHttp = require('chai-http');
const app= require('./app');
chai.use(chaiHttp);
const queryMock =sinon.stub();
const dynamoMock = {
DocumentClient:sinon.fake.returns({
query:queryMock
})
}
let awsDynamoMock;
describe.only('Integration test for activation',()=>{
beforeEach(() => {
awsDynamoMock = sinon.stub(require('aws-sdk'),'DynamoDB');
awsDynamoMock.returns(dynamoMock);
})
afterEach(() => {
awsDynamoMock.restore();
})
it('Request /endpoint returns HTTP 200 with {} when user exist and all task are done',(done)=>{
const params = {
TableName:'table',
KeyConditionExpression: `client_id= :i`,
ExpressionAttributeValues: {
':i': '23424234'
},
ConsistentRead:true
};
const userWithNoPendingsMock = {
Items: [
{
client_id: "23424234",
},
],
Count: 1,
ScannedCount: 1,
}
queryMock.withArgs(params).returns({
promise:() =>sinon.fake.resolves(userWithNoPendingsMock)
})
chai
.request(app)
.post("/endpoint")
.end( (err, res) => {
chai.expect(res.status).to.be.eql(200);
chai.expect(res.body).to.eql({});
done();
});
});
})
Connection to dynamoDB to stub
const AWS = require('aws-sdk');
AWS.config.update({region:'REGION'});
let docClient = false;
const getDynamoSingleton = async () => {
if (docClient) return docClient;
docClient = new AWS.DynamoDB.DocumentClient();
console.log(docClient)
return docClient
}
module.exports = getDynamoSingleton
Using DynamoDB example
const getElementById = async (TableName,key,id)=>{
const docClient = await getDynamoSingleton();
//Make query params.
const params = {
TableName,
KeyConditionExpression: `${key} = :i`,
ExpressionAttributeValues: {
':i': id
},
ConsistentRead:true
};
//Run query as promise.
return docClient.query(params).promise();
}
Im really stuck on this problem, so any help would be useful. I know the problem has something to do with de documentclient
Thanks for the help

Answer 1

I realize this is an old question, but you can set up a resolvable object with a little trickery. Some inspiration from this answer.
const sandbox = require('sinon').createSandbox();
const AWS = require('aws-sdk');
describe('...', () => {
it('...',
 (done) => {
// Create a dummy resolver, which returns an empty object.
const dummy = {func: () => {}};
sandbox.stub(dummy, 'func').resolves({some: 'fake response'});
// Mock docClient.query. Binding to .prototype should make this apply to any `new AWS.DynamoDB.DocumentClient()` calls.
sandbox.stub(AWS.DynamoDB.DocumentClient.prototype, 'query').returns({promise: dummy.func});
// Run your tests here.
});
});
This is cut down to remove a lot of the extra configuration you are doing (and probably need). We create a dummy object with the function func which returns a sinon promise.
Next, we stub the AWS.DynamoDB.DocumentClient prototype so that new AWS.DynamoDB.DocumentClient() will receive our sinon stub.
Third, we configure our DocumentClient prototype stub to return a plain javascript object with a property called promise. This property points to the first dummy object's promise-returning func method.
Now calls to docClient.query(params).promise() should receive a mocked promise. docClient.query(params) will receive the stub sandbox.stub(AWS.DynamoDB.DocumentClient.prototype, ...). And .promise() will be processed from {promise: dummy.func} to refer to the dummy resolver.