How to stub node-cache's cache.get()? - node.js

Question

I'm writing a unit test for a function that uses node-cache.
At the following function,
I want to have a string return at the first cache.get
an array in the second cache.get
Please note that I removed some parts of code from testFunction since it is not relavant to my question.
const NodeCache = require('node-cache');
const cache = new NodeCache();
...
const testFunction = () => {
let myStringCache = cache.get('cacheName1');
let myArrayCache = cache.get('cacheName2');
... Do something with caches ...
return 'return something';
}
...
module.exports = {
...,
testFunction,
...
}
I created the following test
describe('sample test with testFunction() ', ()=>{
let stubCache;
let stub;
before((done)=>{
sandbox = sinon.createSandbox();
stubCache = sandbox.stub(cache, 'get');
stubCache.withArgs('cacheName1').returns('sample string');
stubCache.withArgs('cacheName2').returns([1,2,3,4,5,6]);
stub = proxyquire('./filelocation.js',{
'node-cache': stubCache
});
done();
});
it('should not throw error',(done)=>{
chai.expect(stub.testFunction()).not.to.throw;
});
})
I was Googling around, and there is some partial solution to use proxyquire to stub the value. but looks like it does stub but it's not where I wanted.
It stubs at NodeCache but cache
So I have questions:
Does anybody know how to stub cache.get() with mocha, chai or sinon? If so, please share how you do it ?
Is it possible to stub different returns by the argument of cache.get()?

Answer 1

Here is the unit test solution:
index.js:
const NodeCache = require("node-cache");
const cache = new NodeCache();
const testFunction = () => {
let myStringCache = cache.get("cacheName1");
let myArrayCache = cache.get("cacheName2");
console.log("myStringCache:", myStringCache);
console.log("myArrayCache:", myArrayCache);
return "return something";
};
module.exports = {
testFunction
};
index.spec.js:
const sinon = require("sinon");
const proxyquire = require("proxyquire");
const chai = require("chai");
describe("sample test with testFunction() ", () => {
let stubCache;
let stub;
let getCacheStub;
before(() => {
sandbox = sinon.createSandbox();
getCacheStub = sandbox.stub();
stubCache = sandbox.stub().callsFake(() => {
return {
get: getCacheStub
};
});
getCacheStub.withArgs("cacheName1").returns("sample string");
getCacheStub.withArgs("cacheName2").returns([1, 2, 3, 4, 5, 6]);
stub = proxyquire("./", {
"node-cache": stubCache
});
});
it("should not throw error", () => {
const logSpy = sinon.spy(console, "log");
chai.expect(stub.testFunction()).not.to.throw;
sinon.assert.calledWith(
logSpy.firstCall,
"myStringCache:",
"sample string"
);
sinon.assert.calledWith(logSpy.secondCall, "myArrayCache:", [
1,
2,
3,
4,
5,
6
]);
});
});
Unit test result with 100% coverage:
sample test with testFunction()
myStringCache: sample string
myArrayCache: [ 1, 2, 3, 4, 5, 6 ]
✓ should not throw error
1 passing (87ms)
---------------|----------|----------|----------|----------|-------------------|
File | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s |
---------------|----------|----------|----------|----------|-------------------|
All files | 100 | 100 | 100 | 100 | |
index.js | 100 | 100 | 100 | 100 | |
index.spec.js | 100 | 100 | 100 | 100 | |
---------------|----------|----------|----------|----------|-------------------|
Source code: https://github.com/mrdulin/mocha-chai-sinon-codelab/tree/master/src/stackoverflow/58278211