test_that("warns on invalid input", {
  topic <- RoxyTopic$new()
  topic$add(rd_section("name", "test"))

  expect_snapshot({
    select_args_text(sum, "-xlab:", topic)
    select_args_text(sum, '"a"', topic)
    select_args_text(function(x, y, z) {}, "-x:z", topic)
  })
})

test_that("positive initial values starts from nothing", {
  f <- function(x, y, z) {}

  expect_equal(select_args_text(f, "x y"), c("x", "y"))
})

test_that("negative initial starts from everything", {
  f <- function(x, y, z) {}

  expect_equal(select_args_text(f, "-z"), c("x", "y"))
})

test_that("can alternative exclusion and inclusion", {
  f <- function(x, y, z) {}

  expect_equal(select_args_text(f, "-z z"), c("x", "y", "z"))
  expect_equal(select_args_text(f, "z -z"), character())
})