Add coverage for Windows DLL path helper

Author: t-kalinowski

tests/testthat/test-compiler.R

@@ -74,3 +74,37 @@ test_that("quickr_fcompiler_env writes Makevars when flang is usable", {
   expect_true(startsWith(env, "R_MAKEVARS_USER="))
   expect_true(file.exists(sub("R_MAKEVARS_USER=", "", env, fixed = TRUE)))
 })
+
+test_that("quickr_windows_add_dll_paths updates PATH for Windows-style runs", {
+  temp <- withr::local_tempdir()
+  lib_dir <- file.path(temp, "lib")
+  bin_dir <- file.path(temp, "bin")
+  dir.create(lib_dir, recursive = TRUE)
+  dir.create(bin_dir, recursive = TRUE)
+
+  withr::local_envvar(PATH = "C:\\Existing")
+  expect_true(quickr:::quickr_windows_add_dll_paths(
+    flags = paste0("-L", lib_dir),
+    os_type = "windows"
+  ))
+
+  path <- strsplit(Sys.getenv("PATH"), ";", fixed = TRUE)[[1]]
+  path_norm <- tolower(normalizePath(path, winslash = "\\", mustWork = FALSE))
+  lib_norm <- tolower(normalizePath(lib_dir, winslash = "\\", mustWork = FALSE))
+  bin_norm <- tolower(normalizePath(bin_dir, winslash = "\\", mustWork = FALSE))
+
+  expect_true(lib_norm %in% path_norm)
+  expect_true(bin_norm %in% path_norm)
+  expect_false(quickr:::quickr_windows_add_dll_paths(
+    flags = paste0("-L", lib_dir),
+    os_type = "windows"
+  ))
+})
+
+test_that("quickr_windows_add_dll_paths is a no-op outside Windows", {
+  withr::local_envvar(PATH = "C:\\Existing")
+  expect_false(quickr:::quickr_windows_add_dll_paths(
+    flags = "-Lfoo",
+    os_type = "unix"
+  ))
+})