question: How do you test your services with dependency injection? about typedi

[telega]

One approach is to use Container.set and Container.get in your tests.

@Service()
class MyGlobalClass() {
  foo(){}
}

@Service()
class MyOtherClass( public global: MyGlobalClass) {}

Then in your test, you do

describe('MyOtherClass' , () => {
 it('tests the class', () =>{
 Container.set(MyGlobalClass, {  foo: jest.fn().mockReturnValue(true)}) 
 const otherClass = Container.get(MyOtherClass)
 expect(otherClass.global.foo()).toBe(true)
 })
})

[attilaorosz]

Keep in mind that with @Inject you won't be able to access your injected dependency in the constructor body, the injection is done lazily

[attilaorosz]

Do you clear your container after each test? It could be that the container instanciated your service already, so you setting the dependency of your service does nothing since Container.get will just get back the already created instance anyway.

[attilaorosz]

Container.reset() should do it for you

[tomasz-szymanek]

Yeah, I've tried that with the same effect. No worries mate, I'm done for today anyways, tomorrow I will try some other ideas

Thank you so much

[attilaorosz]

pinging @NoNameProvided for additional ideas

[tomasz-szymanek]

I did exactly that and suddenly it stopped working:

Container.set('example-api-client', new TestApiClient())
const service = Container.get(ServiceUsingExampleApiClient)

console.log(service.exampleApiClient) // original service, not TestApiClient one set using container

I cannot get it to work, and it doesn't have any sense whatsoever to stop working on me like that

[telega]

how are you injecting ExampleApiClient into ServiceUsingExampleApiClient ?

[attilaorosz]

Could you create a repo with this? Its hard to see whats wrong without context.

[tomasz-szymanek]

I cannot publish code from my work, and this is not reproducible since it doesnt work in that one only case, for now I can say that I've tried using Service() via type, and named Service() syntax (Service('name-of-service')) along with @Inject('name-of-service') and it doesnt work in either way.

[tomasz-szymanek]

import 'reflect-metadata'
import { Service } from 'typedi'

@Service('pocket-api-client')
export class PocketApiClient {
  call = async (...args: any[]): Promise<any> => {
    console.log('CALL ORIGINAL')
    return { json: async () => Promise.resolve({ data: 'example', id: '123' }), ok: true }
  }
}

import 'reflect-metadata'
import { Inject, Service } from 'typedi'
import { PocketApiClient } from '../../../../lib/api-client/pocket-api-client'

...

@Service()
export class AddPocketSectionItem {
  @Inject('pocket-api-client')
  public pocketApiClient: PocketApiClient
  constructor() {}
  
  ...

import 'reflect-metadata'
import { Container } from 'typedi'
import { AddPocketSectionItem } from '../services/request'

...

class TestApiClient {
  public call = async (...args) => {
    console.log('CALL TEST')
    return { json: async () => Promise.resolve({ data: 'example', id: '123' }), ok: true }
  }
}

...

describe('POCKET SERVICE add-pocket-section-item', () => {
  it('responds with data fetched from api service', async () => {
    Container.set('pocket-api-client', new TestApiClient())
    const service = Container.get(AddPocketSectionItem)
    
    console.log(service.pocketApiClient) // original pocketApiClient, not TestApiClient

What is funny, is that when I remove type from Inject() statement, it says:

ServiceNotFoundError: Service with "pocket-api-client" identifier was not found in the container. Register it before usage via explicitly calling the "Container.set" function or using the "@Service()" decorator.

Needless to say, I've tried using only Service() and type syntax, without names, and it doesn't work - injected value in AddPocketSectionItem is just undefined

[attilaorosz]

It's weird because it works for me locally. Is there a chance your lib is in a monorepo?

[tomasz-szymanek]

Yes, but other apps are not using any DI containers. It stopped working when I added some new code (unrelated to this), using httpContext for acquiring some headers from each request, and setting getConfig() method in a container via Container.set('get-config', getConfig). It's tested and mockable

import { Config } from 'config'
import { Container } from 'typedi'
import { getConfig } from '../get-config'
import { mockedConfig } from './config-mock'

describe('getConfig method', () => {
  it('responds with generated config', async () => {
    const config = getConfig()

    expect(config).toEqual(mockedConfig)
  })

  it('responds with generated config while using default app name', async () => {
    const config = getConfig('moda')

    expect(config).toEqual(mockedConfig)
  })

  it('is injectable', async () => {
    Container.set('MOCK_GET_CONFIG', getConfig)
    const injectedConfig = Container.get('MOCK_GET_CONFIG') as () => Config
    const config = injectedConfig()

    expect(config).toEqual(mockedConfig)
  })
})

those tests are passing

[attilaorosz]

The problem is the metadata storage of the DI, technically it's tied to your node_modules folder. If your app happens to be in a monorepo that has separate node_module instances for each part, you are kinda out of luck. The Container instance will be different for each. Could you verify if that's the case?

[tomasz-szymanek]

First of all, thanks for your help, it's really kind of you. I verified, my API only uses one exclusive node_modules.

[attilaorosz]

What is funny, is that when I remove type from Inject() statement, it says:

That is expected, if you never reference the class that registers the token it won't be available in the container.

Needless to say, I've tried using only Service() and type syntax, without names, and it doesn't work - injected value in AddPocketSectionItem is just undefined

This is the more interesting part, because if the container is not able to find the token it should throw an error.
The troubling part is that if you mess up the mock registration in the test, it should return the original not undefined.

[tomasz-szymanek]

In test it returns mocked one, in service's body there is undefined, without error

[attilaorosz]

Do you use @Inject or constructor injection?

[tomasz-szymanek]

describe('POCKET SERVICE add-pocket-section-item', () => {
  it('responds with data fetched from api service', async () => {
    Container.set(PocketApiClient, new TestApiClient())
    const service = Container.get(AddPocketSectionItem)
    const mockedApiClient = Container.get(PocketApiClient)

    console.log(service.pocketApiClient) 
    console.log(mockedApiClient)

console.log
    undefined

      at console.log (../../node_modules/@sentry/src/integrations/console.ts:51:1)

  console.log
    TestApiClient { call: [Function (anonymous)] }

      at console.log (../../node_modules/@sentry/src/integrations/console.ts:51:1)

[tomasz-szymanek]

Tried both, it still doesn't work (sorry, I got excited because test passed)

[tomasz-szymanek]

After using constructor injection (without @Inject() decorator) it just injects original dependency instead of mock:

Container.set(PocketApiClient, new TestApiClient())
    const service = Container.get(AddPocketSectionItem)
    const mockedApiClient = Container.get(PocketApiClient)

    console.log(service.pocketApiClient) // original pocketApiClient, not TestApiClient
    console.log(mockedApiClient)

console.log
    PocketApiClient { call: [Function (anonymous)] }

      at console.log (../../node_modules/@sentry/src/integrations/console.ts:51:1)

  console.log
    TestApiClient { call: [Function (anonymous)] }

      at console.log (../../node_modules/@sentry/src/integrations/console.ts:51:1)

[tomasz-szymanek]

@Service()
export class AddPocketSectionItem {
  constructor(public pocketApiClient: PocketApiClient) {}

@Service()
export class PocketApiClient {
call = async (...args: any[]): Promise<any> => {
  console.log('CALL ORIGINAL')
  return { json: async () => Promise.resolve({ data: 'example', id: '123' }), ok: true }
}
}

[tomasz-szymanek]

That ought to be the case here! How do I clear container? I searched in documentation, and I didn't see anything like "reset"

[tomasz-szymanek]

It doesn't work unfortunately, still getting original service instead of mocked one

[attilaorosz]

Just for the sake of the test, could you remove the @Service decorator from PocketApiClient and see what happens?

[tomasz-szymanek]

ServiceNotFoundError: Service with "MaybeConstructable<PocketApiClient>" identifier was not found in the container. Register it before usage via explicitly calling the "Container.set" function or using the "@Service()" decorator.

[attilaorosz]

Ok at this point all I can think of is that something else creates that service for you beforehand somewhere. Could you try to reset the container in the test itself before setting the mock?

[attilaorosz]

You could add a log before the Container.get to make sure it's actually throwing there not beforehand

[tomasz-szymanek]

describe('POCKET SERVICE add-pocket-section-item', () => {
  it('responds with data fetched from api service', async () => {
    Container.reset()
    Container.set(PocketApiClient, new TestApiClient())
    const service = Container.get(AddPocketSectionItem)
    console.log(service.pocketApiClient)
    
    const mockedApiClient = Container.get(PocketApiClient)
    console.log(mockedApiClient)

its respectively undefined and TestApiClient { call: [Function (anonymous)] }

[telega]

maybe as an experiment try changing the implementation of AddPocketSectionItem to

export class AddPocketSectionItem {
  public pocketApiClient = Container.get(PocketApiClient)
  constructor() {}
 

[abhayshiravanthe]

See this
and also, remove all manual mocks of injected dependencies in the test code.
When asserting these injected class's methods in Jest tests, always use jest.spyOn instead of mocking them.

[Edkiri]

One approach is to use Container.set and Container.get in your tests.

@Service()
class MyGlobalClass() {
  foo(){}
}

@Service()
class MyOtherClass( public global: MyGlobalClass) {}

Then in your test, you do

describe('MyOtherClass' , () => {
 it('tests the class', () =>{
 Container.set(MyGlobalClass, {  foo: jest.fn().mockReturnValue(true)}) 
 const otherClass = Container.get(MyOtherClass)
 expect(otherClass.global.foo()).toBe(true)
 })
})

It works for me!
I was also missing the import 'reflect-metadata' in my test file.