Testing controllers (services) with DI for FastifyInstance

Hey!

First of all, thank you for this amazing project!

I’m having a bit of trouble testing a controller which has DI for FastifyInstance, st like this:

@Inject(FastifyInstanceToken)
  private instance!: FastifyInstance;

However, I cant seem to get it working with configureControllerTest:

TypeError: Invalid argument provided for "MyController.instance". Expected class annotated with @Service.

      at injectProperties (lib/decorators/helpers/inject-dependencies.ts:39:19)
      at Object.createWithInjectedDependencies (lib/decorators/helpers/inject-dependencies.ts:29:5)
      at Object.0 (lib/decorators/strategies/controller-type.ts:42:36)
      at instance.register.prefix (lib/decorators/controller.ts:40:85)
      at Plugin.Object.<anonymous>.Plugin.exec (node_modules/avvio/plugin.js:131:17)
      at Boot.loadPlugin (node_modules/avvio/plugin.js:266:10)
      at Task.release (node_modules/fastq/queue.js:143:16)
      at worked (node_modules/fastq/queue.js:195:10)
      at node_modules/avvio/plugin.js:269:7
      at done (node_modules/avvio/plugin.js:201:5)

Also, as a side note, It might be good to mention somewhere in the docs, for whoever is using ts-jest, that they need to properly set up jest environment, i.e. the crucial part:

require('reflect-metadata');

[L2jLiga]

Added an option to access controller instance in tests, also reworked documentation:

https://github.com/L2jLiga/fastify-decorators/blob/v3/docs/Testing.md

[L2jLiga]

I would keep it open to not forget about documentation improvements and returning controller instance