Refactored test utils in VK module

internal/vk/test_sender.go

@@ -0,0 +1,17 @@
+package vk
+
+type testSender struct {
+	sent []testMessage
+}
+
+type testMessage struct {
+	userId  int64
+	message string
+}
+
+func (s *testSender) Send(userId int64, message string) {
+	s.sent = append(s.sent, testMessage{
+		userId:  userId,
+		message: message,
+	})
+}