helper-test --test-type unit generates broken code in Ember 3.11

[Windvis]

It looks like #15609 was merged without also adjusting the helper-test blueprint. Since the helper module no longer exports a named function the generated code is invalid by default.

I'm not sure how this should be solved. Unit tests can still be useful for helpers that return values which are not intended for rendering.

[locks]

I stumbled onto this myself. If you have a function that you want to call outside of the rendering context, my suggestion is to make a util that you can unit test, and that the helper can then import and use and you would still use a rendering test for the helper.

[rwjblue]

I'm not sure how this should be solved. Unit tests can still be useful for helpers that return values which are not intended for rendering.

We should remove the --test-type option for the helper blueprint and associated code.