Hi!
I face similar issue.
In my case, I have a dialog with 3 templates (for header, content and footer) and, during jasmine testing, the templates are not rendered, so, the component HTML template gets rendered like this:
<ejs-dialog _ngcontent-c0="" ...>
<!-- -->
<!-- -->
<!-- -->
</ejs-dialog>
I googled about this, but got no helpful answers...