Should this be an RFC?

• This is not a substantial change

Which package is this a feature request for?

Lit Core (lit / lit-html / lit-element / reactive-element)

Description

Current node build tests are mainly running test files with node and making sure they don't error. This was fine when all we're doing was checking that modules can be imported without throwing, but as we add more situations we want to test that require separate contexts, like testing scenarios when an external DOM shim is already loaded (See #3561), the number of test scripts we have to configure and run starts to grow.

Alternatives and Workarounds

Can re-architect so that we have a single (or maybe 2 for prod and dev node build) node test script that either spawns new processes to test within Node, or via a shell command that can run all node test files, perhaps with a certain prefix.