Fix test for Windows upgrade check.

cmd/soroban-cli/Cargo.toml

@@ -141,3 +141,4 @@ assert_fs = "1.0.7"
 predicates = { workspace = true }
 walkdir = "2.5.0"
 mockito = "1.5.0"
+serial_test = "3.0.0"

cmd/soroban-cli/src/config/data.rs

@@ -202,8 +202,10 @@ fn to_xdr(data: &impl WriteXdr) -> Result<String, xdr::Error> {
 #[cfg(test)]
 mod test {
     use super::*;
+    use serial_test::serial;
 
     #[test]
+    #[serial]
     fn test_write_read() {
         let t = assert_fs::TempDir::new().unwrap();
         std::env::set_var("STELLAR_DATA_HOME", t.path().to_str().unwrap());

cmd/soroban-cli/src/config/upgrade_check.rs

@@ -69,13 +69,18 @@ impl UpgradeCheck {
 #[cfg(test)]
 mod tests {
     use super::*;
+    use serial_test::serial;
     use std::env;
 
     #[test]
+    #[serial]
     fn test_upgrade_check_load_save() {
-        // Set the `XDG_DATA_HOME` environment variable to a temporary directory
+        // Use `STELLAR_DATA_HOME` (cross-platform, highest priority) so that
+        // any `STELLAR_DATA_HOME` or `XDG_DATA_HOME` leaked by parallel tests
+        // cannot shadow our temp dir.
         let temp_dir = tempfile::tempdir().unwrap();
-        env::set_var("XDG_DATA_HOME", temp_dir.path());
+        env::remove_var("XDG_DATA_HOME");
+        env::set_var("STELLAR_DATA_HOME", temp_dir.path());
         // Test default loading
         let default_check = UpgradeCheck::load().unwrap();
         assert_eq!(default_check, UpgradeCheck::default());