From 546541098500a876079b1012b328afe887d51831 Mon Sep 17 00:00:00 2001
From: lightclient <lightclient@protonmail.com>
Date: Wed, 14 Jan 2026 11:51:59 -0700
Subject: [PATCH] rpc: add test for http propagator

---
 rpc/tracing_test.go | 36 ++++++++++++++++++++++++++++++++++--
 1 file changed, 34 insertions(+), 2 deletions(-)

diff --git a/rpc/tracing_test.go b/rpc/tracing_test.go
index 89cd31a075..f32a647e6f 100644
--- a/rpc/tracing_test.go
+++ b/rpc/tracing_test.go
@@ -21,7 +21,9 @@ import (
 	"net/http/httptest"
 	"testing"
 
+	"go.opentelemetry.io/otel"
 	"go.opentelemetry.io/otel/attribute"
+	"go.opentelemetry.io/otel/propagation"
 	sdktrace "go.opentelemetry.io/otel/sdk/trace"
 	"go.opentelemetry.io/otel/sdk/trace/tracetest"
 )
@@ -60,16 +62,33 @@ func newTracingServer(t *testing.T) (*Server, *sdktrace.TracerProvider, *tracete
 
 // TestTracingHTTP verifies that RPC spans are emitted when processing HTTP requests.
 func TestTracingHTTP(t *testing.T) {
-	t.Parallel()
+	// Not parallel: this test modifies the global otel TextMapPropagator.
+
+	// Set up a propagator to extract W3C Trace Context headers.
+	originalPropagator := otel.GetTextMapPropagator()
+	otel.SetTextMapPropagator(propagation.TraceContext{})
+	t.Cleanup(func() { otel.SetTextMapPropagator(originalPropagator) })
+
 	server, tracer, exporter := newTracingServer(t)
 	httpsrv := httptest.NewServer(server)
 	t.Cleanup(httpsrv.Close)
+
+	// Define the expected trace and span IDs for context propagation.
+	const (
+		traceID      = "4bf92f3577b34da6a3ce929d0e0e4736"
+		parentSpanID = "00f067aa0ba902b7"
+		traceparent  = "00-" + traceID + "-" + parentSpanID + "-01"
+	)
+
 	client, err := DialHTTP(httpsrv.URL)
 	if err != nil {
 		t.Fatalf("failed to dial: %v", err)
 	}
 	t.Cleanup(client.Close)
 
+	// Set trace context headers.
+	client.SetHeader("traceparent", traceparent)
+
 	// Make a successful RPC call.
 	var result echoResult
 	if err := client.Call(&result, "test_echo", "hello", 42, &echoArgs{S: "world"}); err != nil {
@@ -92,8 +111,10 @@ func TestTracingHTTP(t *testing.T) {
 		}
 	}
 	if rpcSpan == nil {
-		t.Fatalf("jsonrpc.test/echo span not found.")
+		t.Fatalf("jsonrpc.test/echo span not found")
 	}
+
+	// Verify span attributes.
 	attrs := attributeMap(rpcSpan.Attributes)
 	if attrs["rpc.system"] != "jsonrpc" {
 		t.Errorf("expected rpc.system=jsonrpc, got %v", attrs["rpc.system"])
@@ -107,6 +128,17 @@ func TestTracingHTTP(t *testing.T) {
 	if _, ok := attrs["rpc.jsonrpc.request_id"]; !ok {
 		t.Errorf("expected rpc.jsonrpc.request_id attribute to be set")
 	}
+
+	// Verify the span's parent matches the traceparent header values.
+	if got := rpcSpan.Parent.TraceID().String(); got != traceID {
+		t.Errorf("parent trace ID mismatch: got %s, want %s", got, traceID)
+	}
+	if got := rpcSpan.Parent.SpanID().String(); got != parentSpanID {
+		t.Errorf("parent span ID mismatch: got %s, want %s", got, parentSpanID)
+	}
+	if !rpcSpan.Parent.IsRemote() {
+		t.Error("expected parent span context to be marked as remote")
+	}
 }
 
 // TestTracingBatchHTTP verifies that RPC spans are emitted for batched JSON-RPC calls over HTTP.