feat: Add comprehensive unit tests for CLI and CertificateService, covering command parsing and certificate generation

apps/nxmesh-master/src/db/mod.rs

@@ -9,3 +9,16 @@ pub(crate) async fn establish_connection(
         .await
         .map_err(|e| format!("Failed to connect to database: {}", e).into())
 }
+
+#[cfg(test)]
+mod tests {
+    use super::establish_connection;
+
+    #[tokio::test]
+    async fn establish_connection_fails_for_invalid_url_scheme() {
+        let result = establish_connection("invalid://not-a-db").await;
+        assert!(result.is_err());
+        let msg = result.err().map(|e| e.to_string()).unwrap_or_default();
+        assert!(msg.contains("Failed to connect to database"));
+    }
+}