The "test-th-render" command:

Usage: fossil test-th-render FILE

Read the content of the file named "FILE" as if it were a header or
footer or ticket rendering script, evaluate it, and show the results
on standard output.

Options:

    --cgi                Include a CGI response header in the output
    --http               Include an HTTP response header in the output
    --open-config        Open the configuration database
    --set-anon-caps      Set anonymous login capabilities
    --set-user-caps      Set user login capabilities
    --th-trace           Trace TH1 execution (for debugging purposes)