Add Dropped field for monitoring

ringchan.go

@@ -3,6 +3,9 @@ package ringchan
 type Ring[T any] struct {
 	// C is the channel to receive values from.
 	C <-chan T
+
+	// Number of dropped items due to full buffer.
+	Dropped int
 }
 
 // New creates a ring-buffered channel with fixed capacity from incoming channel.
@@ -29,6 +32,7 @@ func New[T any](in <-chan T, size int) *Ring[T] {
 				default:
 					out <- v
 				}
+				rc.Dropped++
 			}
 		}
 	}()

ringchan_test.go

@@ -33,6 +33,9 @@ func TestRingChanBasic(t *testing.T) {
 	if len(got) != len(want) {
 		t.Fatalf("expected %v values, got %v", len(want), len(got))
 	}
+	if rc.Dropped != 2 {
+		t.Fatalf("expected %d values to be dropped, got %d", 2, rc.Dropped)
+	}
 	for i := range want {
 		if got[i] != want[i] {
 			t.Errorf("expected %v at index %d, got %v", want[i], i, got[i])