fix(node-nest-starter-2020-04-03): backend test commands fail

Problem

The test commands for the backend like

npm test
npm run test:e2e

fail due to different reasons:

npm test due to the DI cannot be resolved:


ts-jest[versions] (WARN) Version 25.1.0 of jest installed has not been tested with ts-jest. If you're experiencing issues, consider using a supported version (>=22.0.0 <24.0.0). Please do not report issues in ts-jest if you are using unsupported versions.
FAIL  src/app.controller.spec.ts
AppController
root
  ✕ should return "API is up and running!" (14ms)

● AppController › root › should return "API is up and running!"

Nest can't resolve dependencies of the AppController (AppService, ?). Please make sure that the argument at index [1] is available in the _RootTestModule context.

  at Injector.lookupComponentInExports (../node_modules/@nestjs/core/injector/injector.js:180:19)

● AppController › root › should return "API is up and running!"

TypeError: Cannot read property 'healthCheck' of undefined

  23 |   describe('root', () => {
  24 |     it('should return "API is up and running!"', () => {
> 25 |       expect(appController.healthCheck()).toBe('API is up and running!');
     |                            ^
  26 |     });
  27 |   });
  28 | });

  at Object.it (app.controller.spec.ts:25:28)

Test Suites: 1 failed, 1 total Tests: 1 failed, 1 total Snapshots: 0 total Time: 2.155s, estimated 3s


2. `npm run test:e2e` it cannot connect to the database although in `npm start run:dev` things work fine. I run it as described in #64 
```sh
> jest --config ./test/jest-e2e.json

ts-jest[versions] (WARN) Version 25.1.0 of jest installed has not been 
tested with ts-jest. If you're experiencing issues, consider using a su
pported version (>=22.0.0 <24.0.0). Please do not report issues in ts-jest if you are using unsupported versions.
[Nest] 94172   - 28/04/2020, 12:17   [MongooseModule] Unable to connect
 to the database. Retrying (1)...
[Nest] 94172   - 28/04/2020, 12:17   [MongooseModule] Unable to connect
 to the database. Retrying (2)... +3007ms
 FAIL  test/app.e2e-spec.ts (7.169s)
  AppController (e2e)
    ✕ / (GET) (5008ms)

  ● AppController (e2e) › / (GET)

    Timeout - Async callback was not invoked within the 5000ms timeout specified by jest.setTimeout.Error: Timeout - Async callback was not invoked within the 5000ms timeout specified by jest.setTimeout.

Generally, I cannot find the expected string 'Hello World!' elsewhere in the code, and after trying the nest starters it seems like a copy-paster from the scaffolder.
Could you provide additional help to set up the testing properly? I'd like to develop in TDD style

akveo / ngx-admin-bundle-support

fix(node-nest-starter-2020-04-03): backend test commands fail #65

Problem