Testing AWS Lambda using Jest and Sinon causing Timeout error - amazon-web-services

Question

I am attempting to execute the following Jest test to test an AWS Lambda locally:
const sinon = require('sinon');
const AWS = require('aws-sdk');
const { handler } = require('../queue_manager.js');
let result = {
// some result
};
let sinonSandbox;
beforeEach((done) => {
sinonSandbox = sinon.createSandbox();
done();
})
afterEach((done) => {
sinonSandbox.restore()
done();
})
it('queue-manager', async () => {
sinonSandbox.stub(AWS.DynamoDB.DocumentClient.prototype, 'get').returns({
promise: function () {
return Promise.resolve(result);
}
});
const lambdaResponse = { code: 200, data: 'some mocked data' };
var callback = function() { };
var context = {}
const event = {
somedata: "data"
};
const actualValue = await handler(event, context, callback);
expect(actualValue).toEqual(result);
});
I am attempting to test processing after a DynamoDB call, however, the test fails with a: Timeout - Async callback was not invoked within the 5000ms timeout specified by jest.setTimeout.Timeout
I tried giving it more time but the same result so it is not that it cannot return successfully in 5 seconds, it is not returning all.
Anyone familiar with Sinon that could possibly point out my issue?

Answer 1

Post edited, fist edition pushed at the bottom of the answer a
Second thought
here is an example on how to test an asynchronous function with Jest
test('the data is peanut butter', done => {
function callback(data) {
try {
expect(data).toBe('peanut butter');
done();
} catch (error) {
done(error);
}
}
fetchData(callback);
});
then I think the missing part in your code is the done callback on the unit test function. could you try this:
it('queue-manager', async (done) => {
sinonSandbox.stub(AWS.DynamoDB.DocumentClient.prototype, 'get').returns({
promise: function () {
return Promise.resolve(result);
}
});
const lambdaResponse = { code: 200, data: 'some mocked data' };
var callback = function() { };
var context = {}
const event = {
somedata: "data"
};
const actualValue = await handler(event, context, callback);
expect(actualValue).toEqual(result);
done();
});
Another option could be to specify the number of assertions (instead of the callback done) :
// before the await handler(...)
expect.assertions(1);
Hope this help.
First lead was the dynamo db ressource hanging:
Quite often the lambda is not returning the result and then runs into timeout because the lambda function is waiting for resources ie: dynamoDB connection for instance.
You can configure the runtime to send the response immediately by setting context.callbackWaitsForEmptyEventLoop to false.
First line of the handler must be:
context.callbackWaitsForEmptyEventLoop = false