Steps to replicate the issue (include links if applicable):

• Create a lua module.
• Call frame:process with wikicode calling subst on a valid template.
• Invoke the module.

What happens?:

• The call remains as plain text.

What should have happened instead?:

• It should invoke subst.

Software version (skip for WMF-hosted wikis like Wikipedia):

Other information (browser name/version, screenshots, etc.): Example