I am trying to test to see if injected service was used within the service I am testing and wondered if that will be possible at all?

public class MyService
{
    private readonly IInjectedService _injectedservice;
    public MyService(IInjectedService injectedService1)
    {
        _injectedservice = injectedService1
    }

    public string Method1(int value)
    {
        _injectedservice.Generate();
    }
}

I have UnitTest to test MyService class, but I want to determine if the InjectedService was used or ran within the MyService. In my test I am mocking the IInjectedService injectedService1 service to pass through