如何模拟OperationContext.Current（WCF消息）

Question

Currently I have a challenge to unit test a production code. We have a function to retrieve an IP address from an incoming WCF messages.

public void DoSomething(){
    var ipAddressFromMessage = GetIpFromWcfMessage();

    var IpAddress = IPAddress.Parse(ipAddressFromMessage);

    if(IpAddress.IsLoopback)
    {
        // do something 
    }
    else
    {
        // do something else
    }
}

private string GetIpFromWcfMessage()
{       
    OperationContext context = OperationContext.Current;
    string ip = ...//use the IP from context.IncomingMessageProperties to extract the ip

    return ip;    
}

The question is, what should I do so that I could test the checking of the IP in the DoSomething() ?

[Test]
Public void DoSomethingTest()
{
    //Arrange...
    // Mock OperationContext so that we can manipulate the ip address in the message

    // Assert.
    ...
}

Should I change the way I use the Operation context in a way so that I can mock it(eg implement an interface and mock the implementation of the interface)?

Answer 1

I would wrap the call with a static helper:

public static class MessagePropertiesHelper
{
  private static Func<MessageProperties> _current = () => OperationContext.Current.IncomingMessageProperties;


  public static MessageProperties Current
  {
      get { return _current(); }
  }

  public static void SwitchCurrent(Func<MessageProperties> messageProperties)
  {
      _current = messageProperties;
  }

}

Then in GetIpFromWcfMessage I would call:

private string GetIpFromWcfMessage()
{       
    var props = MessagePropertiesHelper.Current;
    string ip = ...//use the IP from MessageProperties to extract the ip

    return ip;    
}

And I would be able to switch the implementation in the test scenario:

[Test]
Public void DoSomethingTest()
{
    //Arrange...
    // Mock MessageProperties so that we can manipulate the ip address in the message    
    MessagePropertiesHelper.SwitchCurrent(() => new MessageProperties());

    // Assert.
    ...
}

Here you can find my answer to similar problem: https://stackoverflow.com/a/27159831/2131067 .