test: add unit tests for v2 REPL split_cmd parsing

crates/quicproquo-client/src/client/v2_repl.rs

@@ -924,3 +924,52 @@ pub async fn run_v2_repl(
     client.disconnect();
     Ok(())
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn split_cmd_basic_command() {
+        assert_eq!(split_cmd("/help"), Some(("/help", "")));
+    }
+
+    #[test]
+    fn split_cmd_command_with_args() {
+        assert_eq!(split_cmd("/send hello world"), Some(("/send", "hello world")));
+    }
+
+    #[test]
+    fn split_cmd_leading_whitespace() {
+        assert_eq!(split_cmd("   /quit"), Some(("/quit", "")));
+    }
+
+    #[test]
+    fn split_cmd_non_command() {
+        assert_eq!(split_cmd("hello"), None);
+    }
+
+    #[test]
+    fn split_cmd_empty_input() {
+        assert_eq!(split_cmd(""), None);
+        assert_eq!(split_cmd("   "), None);
+    }
+
+    #[test]
+    fn split_cmd_slash_only() {
+        assert_eq!(split_cmd("/"), Some(("/", "")));
+    }
+
+    #[test]
+    fn split_cmd_args_trimmed() {
+        assert_eq!(split_cmd("/dm    alice"), Some(("/dm", "alice")));
+    }
+
+    #[test]
+    fn split_cmd_special_characters() {
+        assert_eq!(
+            split_cmd("/send hello! @alice #chan"),
+            Some(("/send", "hello! @alice #chan"))
+        );
+    }
+}