add test to round trip an invalid sbp message

rust/sbp2json/tests/test_round_trips.rs

@@ -14,6 +14,61 @@ use common::{
 use crate::common::run_jsonfields2sbp;
 use serde_json::ser::CompactFormatter;
 
+use sbp::json::HaskellishFloatFormatter;
+use serde_json::json;
+
+#[test]
+fn test_invalid_message_round_trip() {
+    // Properly framed data but the payload isn't right given the message type
+    let data: Vec<u8> = vec![0x55, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x65, 0x8D];
+    let mut sbp2json_out: Vec<u8> = Vec::new();
+
+    let mut expected_json = json!({"msg_name": "INVALID", "payload": "VQEBAQEBAWWN"});
+    let expected_json = expected_json.as_object_mut().expect("is a map");
+    let input = Cursor::new(data.clone());
+    let error_handler_opt = converters::ErrorHandlerOptions::CoerceErrorsToInvalidMsg;
+    converters::sbp2json(
+        input,
+        &mut sbp2json_out,
+        HaskellishFloatFormatter {},
+        true,
+        error_handler_opt,
+    )
+    .expect("can run sbp2json");
+
+    let mut out_as_json: serde_json::Value =
+        serde_json::from_str(std::str::from_utf8(&sbp2json_out).expect("is valid utf8"))
+            .expect("is valid JSON");
+
+    for key in &["msg_name".to_string(), "payload".to_string()] {
+        assert!(expected_json.get(key).is_some());
+        assert_eq!(
+            out_as_json.as_object_mut().and_then(|m| m.remove(key)),
+            expected_json.clone().remove(key),
+            "{key} values must be equal"
+        );
+    }
+    assert!(
+        out_as_json
+            .as_object()
+            .map(|m| m.is_empty())
+            .unwrap_or(false),
+        "out object should contain no additional keys"
+    );
+
+    let mut json2sbp_out: Vec<u8> = Vec::new();
+
+    converters::json2sbp(
+        Cursor::new(sbp2json_out),
+        &mut json2sbp_out,
+        true,
+        error_handler_opt,
+    )
+    .expect("can run json2sbp");
+
+    assert_eq!(data, json2sbp_out, "completed round trip");
+}
+
 #[test]
 fn test_stop_on_error() {
     let root = find_project_root().unwrap();