test_that("file_extension works", {
  # returns empty string with no extension
  expect_equal(file_extension("README"), "")
  expect_equal(file_extension("file."), "")
  expect_equal(file_extension("path/to/file"), "")

  # extracts extension correctly
  expect_equal(file_extension("script.r"), "r")
  expect_equal(file_extension("path/to/script.R"), "r")
  expect_equal(file_extension("path.to/script.py"), "py")
  expect_equal(file_extension("script.tar.gz"), "gz")

  # handles special characters in path
  expect_equal(file_extension("file with spaces.txt"), "txt")
  expect_equal(file_extension("path/with.dots/file.md"), "md")
})

test_that("default_gander_style returns expected text", {
  expect_match(
    default_gander_style(),
    "Use tidyverse style and, when relevant, tidyverse packages",
    fixed = TRUE
  )
})

test_that("get_gander_style returns default when no option set", {
  withr::local_options(.gander_style = NULL)
  expect_equal(get_gander_style(), default_gander_style())
})

test_that("get_gander_style returns option when set", {
  withr::local_options(.gander_style = "Use base R style.")
  expect_equal(get_gander_style(), "Use base R style.")
})

test_that("get_gander_style validates option value", {
  withr::local_options(.gander_style = 1)
  expect_snapshot(get_gander_style(), error = TRUE)

  withr::local_options(.gander_style = c("a", "b"))
  expect_snapshot(get_gander_style(), error = TRUE)
})