Add setup for user cache directory in tests to prevent pak subprocess failures

Author: e-kotov

tests/testthat/setup-pak.R

@@ -0,0 +1,7 @@
+# pak (via pkgcache) requires a user cache directory.
+# In CI environments or during R CMD check, this might not be set,
+# causing pak subprocesses to fail.
+if (Sys.getenv("R_USER_CACHE_DIR") == "") {
+  # Use a temporary directory for the cache during tests
+  Sys.setenv(R_USER_CACHE_DIR = tempfile("pak-cache-"))
+}