set-main-contributors.md
In plume: A Simple Author Handler for Scientific Writing

set_ranks() gives meaningful error messages

Code
  (expect_error(aut$set_main_contributors()))
Output
  <error/rlang_error>
  Error:
  ! `...` must not be empty.
Code
  (expect_error(aut$set_main_contributors(1, .roles = 1)))
Output
  <error/rlang_error>
  Error:
  ! `.roles` must be a character vector.
Code
  (expect_error(aut$set_main_contributors(1, .roles = c("x", "x"))))
Output
  <error/rlang_error>
  Error:
  ! `.roles` must have unique input values.
Code
  (expect_error(aut$set_main_contributors(1, .by = 1)))
Output
  <error/rlang_error>
  Error:
  ! `.by` must be a character string.