feat: complete cmpp gateway delivery recovery workflows

gateway/internal/upstream/connection_loss_test.go

@@ -0,0 +1,50 @@
+package upstream
+
+import (
+	"errors"
+	"testing"
+)
+
+func TestHandleConnectionLossNotifiesPendingSubmitters(t *testing.T) {
+	conn := &connection{
+		pending: make(map[uint32]chan submitPartResponse),
+	}
+	waiter := make(chan submitPartResponse, 1)
+	conn.pending[7] = waiter
+
+	loss := errors.New("socket closed")
+	conn.handleConnectionLoss(loss)
+
+	select {
+	case result := <-waiter:
+		if !errors.Is(result.err, loss) {
+			t.Fatalf("pending waiter err = %v, want %v", result.err, loss)
+		}
+	default:
+		t.Fatal("expected pending waiter to be notified")
+	}
+
+	if !conn.closed {
+		t.Fatal("expected connection to be marked closed")
+	}
+	if len(conn.pending) != 0 {
+		t.Fatalf("expected pending map to be reset, got %d entries", len(conn.pending))
+	}
+}
+
+func TestTemporaryReadTimeoutDetection(t *testing.T) {
+	if !isTemporaryReadTimeout(fakeNetError{timeout: true}) {
+		t.Fatal("expected timeout error to be treated as temporary")
+	}
+	if isTemporaryReadTimeout(errors.New("eof")) {
+		t.Fatal("did not expect non-timeout error to be treated as temporary")
+	}
+}
+
+type fakeNetError struct {
+	timeout bool
+}
+
+func (f fakeNetError) Error() string   { return "network error" }
+func (f fakeNetError) Timeout() bool   { return f.timeout }
+func (f fakeNetError) Temporary() bool { return f.timeout }