Jest doMock the same method multiple times - node.js

Question

I would like to test following part of the code:
// ... code above
const created = async payload => {
const model = await db.collection('models').doc(payload.model)
.get() // <--- 1st .get() occurence
if (!model.exists) {
// Add product to the orphans collection
await db.collection('orphans').doc(payload.sku).set(payload)
} else {
// Grab the categories field
const categories = model.get('categories') // <--- 2nd .get() occurence
// Product is either empty or does not exists at all
if (!categories || categories.length < 1) {
// Add product to the orphans collection
await db.collection('orphans').doc(payload.sku).set(payload)
} else {
// Otherwise remove from the orphans collection
await deleted(payload.sku)
}
}
}
I do not know how to properly mock the file twice in the same callback. Here is what I get:
test.only('it should react when an event "created" has been fired', async () => {
const spy = jest.fn()
jest.doMock('#google-cloud/firestore', () => class {
collection () {
return {
doc: () => {
return {
get: () => {
return {
exists: () => {
spy()
}
}
},
set: () => {
spy()
}
}
}
}
}
})
const observer = require('./product')
await observer('created', {})
await expect(spy.mock.calls.length).toBe(1)
})
I get this error:
● it should react when an event "created" has been fired
TypeError: model.get is not a function
25 | } else {
26 | // Grab the categories field
> 27 | const categories = model.get('categories')
| ^
28 |
29 | // Product is either empty or does not exists at all
30 | if (!categories || categories.length < 1) {
at created (app/observers/product.js:27:30)
at Object.<anonymous>.module.exports (app/observers/product.js:6:28)
at Object.<anonymous> (app/observers/product.spec.js:34:3)
Test Suites: 1 failed, 1 total
Tests: 1 failed, 1 skipped, 2 total
Snapshots: 0 total
Time: 0.147 s, estimated 1 s
Ran all test suites matching /app\/observers\/product.spec.js/i.
What is the working solution to test two scenarios of the same mocked get() method ?

Answer 1

In your code :
const model = await db.collection('models').doc(payload.model)
.get() // <--- 1st .get() occurence
If we look at your mock, the get method of doc returns :
{
exists: () => {
spy()
}
}
There are no property named get, so it is undefined (and not a function).
I guess you just have to change this part to :
{
exists: true, // can be false
get: spy,
}
And your problem should be solved.
Btw, you can also change the mock of set method to set: spy. Or you can keep it to set: () => { spy() }, but you should at least return the value if you want to mock it : set: () => { spy() }.
Now, about how to properly mock multiple times, here's what you can do :
const observer = require('./product')
const spyGet = jest.fn()
const spySet = jest.fn() // I like having different mocks, if one function use get & set, tests will be clever & more readable if you use different spies
describe('on event "created" fired', () => {
const categories = []
beforeEach(() => {
// I put mocks here to make test more readable
jest.doMock('#google-cloud/firestore', () => class {
collection () {
return {
doc: () => {
return {
get: () => {
return {
exists: true,
get: spyGet,
}
},
set: spySet
}
}
}
}
})
spyGet.mockResolvedValueOnce(categories) // you can also use mockResolvedValue, but mockResolvedValueOnce allow you to mock with different values on the same test & same mock
})
it.only('should get categories', async () => {
await observer('created', {})
// here's all the ways you can test it
expect(spyGet).toBeCalledTimes(1)
expect(spyGet.mock.calls.length).toBe(1)
expect(spyGet).toBeCalledWith('categories')
expect(spyGet).toHaveBeenNthCalledWith(1, 'categories')
})
})
Note : You should reset & clear your mocks between tests manually (in a afterEach or beforeEach) if you don't set it into jest config.