Thanks for reaching out @psousa50. I’m one of the maintainers for dbt-core, and I can answer your question.
Here’s the source code for the render jinja context member:
And here’s a little bit of explanation about get_rendered.
While I’m not aware of us advertising render as a public interface, it’s extremely unlikely to change anytime soon. So you should be safe to use it within the dbt-unit-testing package.
Hope this helps!
Side note: @joellabes is dbt folk, he just wanted to be careful about making promises since this is deep within the internals.