How to run LB3 app tests when the app is mounted in a LB4 project

[kevintc]

Steps to reproduce

Migration from lb3 to lb4, our legacy app lives in ./lb3app and tests (using Mocha) are in ./lb3app/tests

Current Behavior

In ./lb3app/tests/main.js, we have const app = require('../server/server').
When trying to run the tests using mocha ./lb3app/tests/main.js app is undefined.

I tried typescript-require and:

const { ApiApplication } = require('../../src/index.ts')
const app = new ApiApplication()

Expected Behavior

I expected a way to call the new lb4 app object from lb3 tests framework.
Or do we need to write all the tests again in .ts?

Link to reproduction sandbox

Our current setup is close to this one: https://github.com/strongloop/loopback-next/tree/master/examples/lb3-application
I'll see if I can add mocha to it.

Additional information

node -e 'console.log(process.platform, process.arch, process.versions.node)':

darwin x64 10.16.0

npm ls --prod --depth 0 | grep loopback:

├── @loopback/boot@1.5.8
├── @loopback/booter-lb3app@1.3.2
├── @loopback/context@1.23.2
├── @loopback/core@1.10.4
├── @loopback/openapi-v3@1.9.9
├── @loopback/repository@1.15.1
├── @loopback/rest@1.20.1
├── @loopback/rest-explorer@1.4.1
├── @loopback/service-proxy@1.3.8
├── loopback@3.26.0
├── loopback-boot@3.3.1
├── loopback-component-explorer@6.4.0
├── loopback-component-oauth2@3.2.0
├── loopback-component-passport@3.10.0
├── loopback-connector-es@1.4.1
├── loopback-connector-mongodb@3.9.2
├── loopback-connector-mysql@2.4.1
├── loopback-connector-rest@3.5.0
├── loopback-context@3.4.0

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[dhmlau]

@nabdelgadir, could you please take a look? Thanks!

[nabdelgadir]

Hi @kevintc, can you try:

const {ApiApplication} = require('../../')
const app = new ApiApplication()

[bajtos]

@kevintc thank you for starting this discussion.

First of all, why would you like to access LB4 application from your LB3 tests? In my mind, this creates a cyclic dependency (LB4 app depends on LB3 app, but your LB3 tests want to depend on LB4 app).

Having said that, I think we didn't consider how to run LB3 app tests when the app is mounted in a LB4 project, so I am not surprised there are rough edges now.

[romain-ortega]

Hey, thanks for your answers @bajtos @nabdelgadir !

We managed to make tests work by booting both LB4 app (@nabdelgadir method 👍) and LB3 app (via require ../server/server)

With LB4 Application we can retrieve open API spec and execute our end-to-end tests.

However, we were wondering if there is a way to access our LB3 methods directly from LB4 application, without requiring LB3 server manually ?

[nabdelgadir]

However, we were wondering if there is a way to access our LB3 methods directly from LB4 application, without requiring LB3 server manually ?

Sorry for the super delayed response! Do you have an example of a LB3 method that you'd want to access directly?