test: update message preparation tests to expect explicit User role markers

internal/util/messages_test.go

@@ -12,7 +12,7 @@ func TestMessagesPrepareBasic(t *testing.T) {
 	if got == "" {
 		t.Fatal("expected non-empty prompt")
 	}
-	if got != "Hello" {
+	if got != "<｜User｜>Hello" {
 		t.Fatalf("unexpected prompt: %q", got)
 	}
 }
@@ -55,7 +55,7 @@ func TestMessagesPrepareArrayTextVariants(t *testing.T) {
 		},
 	}
 	got := MessagesPrepare(messages)
-	if got != "line1\nline2" {
+	if got != "<｜User｜>line1\nline2" {
 		t.Fatalf("unexpected content from text variants: %q", got)
 	}
 }

internal/util/util_edge_test.go

@@ -162,13 +162,16 @@ func TestMessagesPrepareMergesConsecutiveSameRole(t *testing.T) {
 		{"role": "user", "content": "World"},
 	}
 	got := MessagesPrepare(messages)
+	if !strings.HasPrefix(got, "<｜User｜>") {
+		t.Fatalf("expected user marker at the start, got %q", got)
+	}
 	if !strings.Contains(got, "Hello") || !strings.Contains(got, "World") {
 		t.Fatalf("expected both messages, got %q", got)
 	}
-	// Should be merged without <｜User｜> between them
+	// Should be merged into a single user turn with one marker at the start.
 	count := strings.Count(got, "<｜User｜>")
-	if count != 0 {
-		t.Fatalf("expected no User marker for first message pair, got %d occurrences", count)
+	if count != 1 {
+		t.Fatalf("expected one User marker for the merged pair, got %d occurrences", count)
 	}
 }