Use `{withr}` to create temporary files (that are automatically deleted) in tests

[André Veríssimo]

Simplifies tests by removing manual creation and action to remove on exit.

• local_file(): for tests defining a specific name
• local_tempfile(): when creating generic temporary file without any name requirement

Example:

diff --git a/tests/testthat/test-write.R b/tests/testthat/test-write.R
index d53c7eb..d3b1e99 100644
--- a/tests/testthat/test-write.R
+++ b/tests/testthat/test-write.R
@@ -1,20 +1,14 @@
 data_to_save <- dplyr::tibble(X = c(1, 2, NA), Y = c("a", "", "c"), Z = c(1, 2, 3))
 
 test_that("xportr_write: exported data can be saved to a file", {
-  tmpdir <- tempdir()
-  tmp <- file.path(tmpdir, "xyz.xpt")
-
-  on.exit(unlink(tmpdir))
+  tmp <- local_file("xyz.xpt")
 
   xportr_write(data_to_save, path = tmp)
   expect_equal(read_xpt(tmp), data_to_save)
 })
@@ -64,15 +52,10 @@ test_that("xportr_write: exported data can be saved to a file with a existing me
 })
 
 test_that("xportr_write: expect error when invalid multibyte string is passed in label", {
-  tmpdir <- tempdir()
-  tmp <- file.path(tmpdir, "xyz.xpt")
-
-  on.exit(unlink(tmpdir))
-
   expect_error(
     xportr_write(
       data_to_save,
-      tmp,
+      local_file("xyz.xpt"),
       metadata = data.frame(
         dataset = "data_to_save",
         label = "Lorizzle ipsizzle dolizzl\xe7 pizzle"