This test is a safety check, ensuring that all @NgModule's exported by Angular framework packages can be imported in user code without causing any build errors.

Occasionally, an @NgModule might re-export another module. This is fine, but there are cases, especially with relative imports being used, where the compiler (in consuming projects) is not able to find a working import to these re-exported symbols.

The re-exported symbols simply need to be re-exported from the entry-point. For more details on this, see: angular/components#30667.