If you're running an application and need to access the binary messenger before runApp() has been called (for example, during plugin initialization), then you need to explicitly call the WidgetsFlutterBinding.ensureInitialized() first.
If you're running a test, you can call the TestWidgetsFlutterBinding.ensureInitialized() as the first line in your test's main() method to initialize the binding.
Follow is the error log
If you're running an application and need to access the binary messenger before
runApp()has been called (for example, during plugin initialization), then you need to explicitly call theWidgetsFlutterBinding.ensureInitialized()first. If you're running a test, you can call theTestWidgetsFlutterBinding.ensureInitialized()as the first line in your test'smain()method to initialize the binding.