rmd_select-has_heading.md
In parsermd: Formal Parser and Related Tools for R Markdown Documents

has_heading validates input comprehensively

i In argument: `has_heading(123)`.
Caused by error in `has_heading()`:
! Assertion on 'heading' failed: Must be of type 'character', not 'double'.

i In argument: `has_heading(NULL)`.
Caused by error in `has_heading()`:
! Assertion on 'heading' failed: Must be of type 'character', not 'NULL'.

i In argument: `has_heading(character(0))`.
Caused by error in `has_heading()`:
! Assertion on 'heading' failed: Must have length >= 1, but has length 0.

i In argument: `has_heading(c("valid", NA))`.
Caused by error in `has_heading()`:
! Assertion on 'heading' failed: Contains missing values (element 2).