Although you don't say it I am assuming that you want to be able to host both the fake and the real service in a single applcation. If so you can host more than one WCF service in a single application. In order to do so you will need to change the code so that it creates more than one host.
Code change
class Program
{
static void Main(string[] args)
{
ServiceHost host1 = new ServiceHost(typeof(Calculator));
host1.Open();
ServiceHost host2 = new ServiceHost(typeof(Calculator_Fake));
host2.Open();
Console.ReadLine();
}
}
Config change
<endpoint address="http://localhost:8000/CalService"
binding="basicHttpBinding"
contract="WCF_Service.ICalculator" />
<endpoint address="http://localhost:8000/FakeCalService"
binding="basicHttpBinding"
contract="WCF_Service.ICalculator" />