How to use sinon to stub aws-param-store getParametersByPath() - node.js

Question

I'm using the package aws-param-store and I'm trying to write Unit tests
that stub calls to getParametersByPath().
Package can be found here:
https://www.npmjs.com/package/aws-param-store
Here is my sinon code to stub the call. The function getParametersByPath is an async function
so I'm trying to return a resolved promise to stub it:
const awsParameterStore = require('aws-param-store');
const sinon = require("sinon");
let sandbox = sinon.createSandbox();
// In My Test:
let parms = new Map();
parms.set("key1","value1");
parms.set("key2","value2");
sandbox.stub(awsParameterStore,'getParametersByPath').callsFake(async function(prefix){
console.log("INSIDE STUB for getParametersByPath:" + prefix);
return Promise.resolve(parms);
});
My app makes a call to the function like this:
let parameters = await awsParameterStore.getParametersByPath("/foo");
However, instead of getting back the Map of dummy parameters, I get an empty object {}.
I can see that the stub is getting called.
Any ideas on how to properly stub this so I can return some dummy parameters in my unit tests?
Thanks!

Answer 1

I tried to check your code, and it's completely fine.
import test from 'ava'
const awsParameterStore = require('aws-param-store');
const sinon = require('sinon')
test('test stub', async t => {
let parms = new Map();
parms.set("key1","value1");
parms.set("key2","value2");
parms.set("key3","value3");
parms.set("key4","value4");
sinon.stub(awsParameterStore, 'getParametersByPath').callsFake(async function(prefix){
console.log("INSIDE STUB for getParametersByPath:" + prefix)
return Promise.resolve(parms);
})
const res = await awsParameterStore.getParametersByPath('/some-prefix')
console.log(JSON.stringify(res))
res.forEach((value, key) => {
console.log(`[${key}]= ${value}`)
})
t.true(true)
})
What is weir:
console.log - show that result is {}
but if you debug or log the value one by one, you can see that stub works fine:
Debugger attached.
INSIDE STUB for getParametersByPath:/some-prefix
{}
[key1]= value1
[key2]= value2
[key3]= value3
[key4]= value4
✔ test stub
UPD: problem is how to log Map by JSON.stringify(). So, you must log the map as:
console.log(JSON.stringify([...res]))

Answer 2

Here is the unit test solution:
index.js:
const awsParameterStore = require('aws-param-store');
async function main() {
let parameters = await awsParameterStore.getParametersByPath('/foo');
return parameters;
}
module.exports = main;
index.test.js:
const main = require('./');
const sinon = require('sinon');
const awsParameterStore = require('aws-param-store');
const { expect } = require('chai');
let sandbox = sinon.createSandbox();
describe('59787603', () => {
it('should pass', async () => {
let parms = new Map();
parms.set('key1', 'value1');
parms.set('key2', 'value2');
sandbox.stub(awsParameterStore, 'getParametersByPath').resolves(parms);
const actual = await main();
expect(actual).to.be.eql(parms);
});
});
Unit test results with 100% coverage:
59787603
✓ should pass
1 passing (11ms)
----------|---------|----------|---------|---------|-------------------
File | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s
----------|---------|----------|---------|---------|-------------------
All files | 100 | 100 | 100 | 100 |
index.js | 100 | 100 | 100 | 100 |
----------|---------|----------|---------|---------|-------------------
source code: https://github.com/mrdulin/expressjs-research/tree/master/src/stackoverflow/59787603