C#

public class AccountServices
{
    ICurrencyServices currencyService = null;
    public AccountServices(ICurrencyServices services)
    {
        currencyService = services;
    }

    public string Total()
    {
        return "10" + currencyService.GetTotal();
    }
}

public class CurrencyServices : ICurrencyServices
{
    public string GetTotal()
    {
        return "10";
    }
}

public interface ICurrencyServices
{
    string GetTotal();
}

[Test]
public void TestTotal()
{
    Mockery mock = new Mockery();
    ICurrencyServices currency = mock.NewMock<icurrencyservices>();
    Expect.Once.On(currency).Method("GetTotal").Will(Return.Value("100"));
    AccountServices services = new AccountServices(currency);
    Assert.AreEqual("10100", services.Total());
}</icurrencyservices>

AccountServices services = new AccountServices(currency);
Assert.AreEqual("10100", services.Total());
Assert.AreEqual("10100", services.Total());// This will throw exception

"unexpected invocation of currencyservices.GetTotal()"

class CLocker
{
    [DllImport("user32.dll")]       static extern int       GetThreadDesktop(int dwThread);
    [DllImport("kernel32.dll")]     static extern bool      CreateProcess(string lpApplicationName, string lpCommandLine, IntPtr lpProcessAttributes, IntPtr lpThreadAttributes, bool bInheritHandles, int dwCreationFlags, IntPtr lpEnvironment, string lpCurrentDirectory, ref STARTUPINFO lpStartupInfo, ref PROCESS_INFORMATION lpProcessInformation);
}