test: cover RPC secret trimming fallback (#2796)

Signed-off-by: 安正超 <anzhengchao@gmail.com>
Co-authored-by: houseme <housemecn@gmail.com>
Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

crates/credentials/src/credentials.rs

@@ -558,6 +558,32 @@ mod tests {
         );
     }
 
+    #[test]
+    fn test_resolve_rpc_secret_trims_and_falls_back_from_blank_env() {
+        assert_eq!(
+            resolve_rpc_secret(Some("  custom-rpc-secret  "), None).as_deref(),
+            Some("custom-rpc-secret")
+        );
+        assert_eq!(
+            resolve_rpc_secret(Some(""), Some("custom-global-secret")).as_deref(),
+            Some("custom-global-secret")
+        );
+        assert_eq!(
+            resolve_rpc_secret(Some("  "), Some("  custom-global-secret  ")).as_deref(),
+            Some("custom-global-secret")
+        );
+        assert_eq!(
+            resolve_rpc_secret(Some("  "), Some("custom-global-secret")).as_deref(),
+            Some("custom-global-secret")
+        );
+    }
+
+    #[test]
+    fn test_resolve_rpc_secret_returns_none_for_trimmed_default_secret() {
+        let padded_default_secret = format!("  {}  ", DEFAULT_SECRET_KEY);
+        assert!(resolve_rpc_secret(Some(padded_default_secret.as_str()), Some("custom-global-secret")).is_none());
+    }
+
     #[test]
     fn test_masked_debug() {
         // Test None