How to execute only one test spec with angular-cli

Question

I have Angular2 project build with Angular-CLI (beta 20).

Is there a way to run tests against only one selected spec file?

I used to have a project based on

Answer 1

This worked for me in every case:

ng test --include='**/dealer.service.spec.ts'

However, I usually got "TypeError: Cannot read property 'ngModule' of null" for this:

ng test --main src/app/services/dealer.service.spec.ts

Version of @angular/cli 10.0.4