Define and register a base class

It just needs to inherit from Spec::Example::ExampleGroup so it’s runnable.

require 'spec/example/example_group'
class UnitTest < Spec::Example::ExampleGroup
   protected
   def you_can_call_this
   end
end

Spec::Example::ExampleGroupFactory.register(:unit_test, UnitTest)

Set the type when describing

describe 'By supplying the :type', :type => :unit_test do
    it 'this example group inherits from whatever class you supply as :type' do
        self.protected_methods.should include('you_can_call_this')
    end
end

You now have common base class to your specifications.

But perhaps I should not have been surprised. After all, if you are truly test driving, how could you possibly leave anything uncovered?

Here’s what it looked like to begin with (an arrow means depends on):

Mp3HashController
|---------------> TrackFileFinder
|---------------> StreamHasher
|---------------> Log

Operation:

• Take input of trackid and format id (both numbers)
• Open a stream on the file
• Supply that stream to the StreamHasher
• Return the hash as text to user

Next requirement — learning file hashes

This works as required but we can improve performance by reducing the number of times we calculate a file’s hash. Assuming each file is static — i.e., its MP3 frames will never change — then we only need to calculate its hash once.

Rather than do this every time, we could save the result somewhere — a database perhaps. Which means we are introducing new behaviour.

When producing a hash, first check whether it already exists
If it does exist, then return it
Otherwise generate it and store it for next time

We could naively add a new HashRepository collaborator:

Mp3HashController
|---------------> TrackFileFinder
|---------------> StreamHasher
|---------------> Log
|---------------> HashRepository

But now our interface is expanding, this has a habit of getting out of control and you can end up with ten constructor arguments. This is commonly known as the “Too Many Dicks on the Dance Floor” problem.

So what’s wrong with it?

• Mp3HashController is no longer composing its behaviour from one layer of abstraction. This notion of learning return values has changed that. It is now exposed to details it shouldn’t have any knowledge of let alone dependency on.
• Mp3HashController is now more difficult to test, there are more paths that have to exercised though the same interface
• There is new conditional behaviour here that clearly belongs on its own — clients should not even know this is happening
• It is much easier to test the learning behaviour on its own — I shouldn’t have to probe a controller
• I shouldn’t have to describe an object’s behaviour in terms of another objects interface, I should be able to use that object directly
• I would likely have to suppress some behaviour(s) while testing others. This will be manifest itself as complicated stubbing
• Lots of dependent stubbing. Each of those collaborators are actually collaborators themselves. I think this is a smell. I shouldn’t have to consider this when unit testing Mp3HashController.

There is an opportunity to introduce an abstraction here. If we consider that all Mp3HashController requires is something to get a hash, then we can actually reduce it to:

Mp3HashController
|---------------> Log
|---------------> HashRepository

And then we have a HashRepository implementation like this:

LearningHashRepository
|---------------> TrackFileFinder
|---------------> StreamHasher
|---------------> HashRepository

The LearninghHashRepository has the responsibility of storing any hashes that don’t exist.

This could probably be condensed even further. TrackFileFinder and StreamHasher represent the concept of obtaining the hash of a file given a track identifier, so they can be combined. This reduces LearningHashRepository to a sort of write-through cache.

If it seems you can’t (i.e., your password is rejected) then you  most likely need to export your user accounts and groups so cygwin can see them.

Another clue that you need to export is if you get a message like:

Your group is currently "mkpasswd".  This indicates that
the /etc/passwd (and possibly /etc/group) files should be rebuilt.
See the man pages for mkpasswd and mkgroup then, for example, run
mkpasswd -l [-d] > /etc/passwd
mkgroup  -l [-d] > /etc/group
Note that the -d switch is necessary for domain users.

To export domain users:

$ mkpasswd -d >> /etc/passwd

To export groups:

$ mkgroup > /etc/group

Troubleshooting

Errors logging in as domain user

2 [main] -bash 31884 C:\cygwin\bin\bash.exe: ***
    fatal error - couldn't dynamically determine load address for 'WSAGetLastError'
    (handle 0xFFFFFFFF), Win32 error 126
Connection to localhost closed.

This is because the cygwin sshd service must also run as domain account. I solved this by changing the user to my domain account.

An extension method is nothing more than a compiler trick. It is simply a static method that takes an instance of the type being extended as an argument. That’s it.

The sugar part is that to you as a programmer, it appears to read more naturally in some cases.

They do not have any special privileges on private or protected members and they are not analagous to ruby module mixins (because the extended class cannot invoked extension methods).

[TBD: It is interesting that instance methods are supplied "this" as their first argument, see CIL]

[TBD: It is interesting that the compiler emits a callvirt instruction even in cases where call seems more appropriate just because callvirt has a null reference check. See: Why does C# always use callvirt?]

[TBD: Extensions are really a higher level abstraction because they operate only against public interface. An extension method is a client of the object it "extends"]

Example

namespace Examples {
    public class ExampleClass { }

    public static class Extensions {
        public static void ExtensionMethod(this ExampleClass instance) {
            instance.ToString();
        }
    }

    public class ThatUsesExampleClass {
        public void RunExample() {
            new ExampleClass().ExtensionMethod();
        }
    }
}

public void RunExample() {
    new ExampleClass().ExtensionMethod();
}

.method public hidebysig instance void
RunExample() cil managed
{
    // Code size       13 (0xd)
    .maxstack  8
    IL_0000:  nop
    IL_0001:  newobj     instance void Examples.ExampleClass::.ctor()
    IL_0006:  call       void Examples.Extensions::ExtensionMethod(class Examples.ExampleClass)
    IL_000b:  nop
    IL_000c:  ret
} // end of method ThatUsesExampleClass::RunExample

It is clear that the compiler has done nothing more than redirect to a static method on a static class:

IL_0006:  call       void Examples.Extensions::ExtensionMethod(class Examples.ExampleClass)

Usage

The usual static method usage rules apply:

[Clean code chapter 6]
Procedural code (code using data structures) makes it easy to add new functions withoutchanging the existing data structures. OO code, on the other hand, makes it easy to add new classes without changing existing functions.

The complement is also true:
Procedural code makes it hard to add new data structures because all the functions must
change. OO code makes it hard to add new functions because all the classes must change.
So, the things that are hard for OO are easy for procedures, and the things that are
hard for procedures are easy for OO!

In any complex system there are going to be times when we want to add new data
types rather than new functions. For these cases objects and OO are most appropriate. On
the other hand, there will also be times when we’ll want to add new functions as opposed
to data types. In that case procedural code and data structures will be more appropriate.

Mature programmers know that the idea that everything is an object is a myth. Sometimes
you really do want simple data structures with procedures operating on them.

Back to the question

Still no answer.

But I can’t see any reason why the C# compiler couldn’t do the same for static constructs, but I wonder how you would express that on the extension method itself.  Perhaps that’s where the ExtensionAttribute comes in. Note: It currently is illegal to use the ExtensionAttribute directly.

But if you examine the IL for an extension method itself, you’ll see it has been applied:

.custom instance void [System.Core]System.Runtime.CompilerServices.ExtensionAttribute::.ctor() =
    ( 01 00 00 00 )
.method public hidebysig static void
    ExtensionMethod(class Examples.ExampleClass 'instance') cil managed {

    .custom instance void [System.Core]System.Runtime.CompilerServices.ExtensionAttribute::.ctor() =
        ( 01 00 00 00 ) 

    // Code size       9 (0x9)
    .maxstack  8
    IL_0000:  nop
    IL_0001:  ldarg.0
    IL_0002:  callvirt   instance string [mscorlib]System.Object::ToString()
    IL_0007:  pop
    IL_0008:  ret
} // end of method Extensions::ExtensionMethod

Redirection

It appears this does not work as expected, i.e. you can’t redirect stdout from an interactive ftp session to local file. It creates the file but with nothing in it.

Solution is to run ftp with the -s option which specifies a file containing the full list of commands to be run (including log-in).

> ftp -s:commands.txt > out/result.txt

Where your commands list looks like this example that prints the contents of a directory called phils_lunchbox :

open host_or_ip_address port
username
Password
cd phils_lunchbox
ls -l
quit

Tips

References

Scenario 1: Warm Teapot

Given a Kettle of Boiling Water
When Boiling Water is poured in to the Teapot
Then it should* warm the Teapot

Scenario 2: Brewing the tea

Given a Kettle of Boiling Water
And 5 Teabags
When 5 Teabags are placed in the Teapot
And Boiling Water is poured in to the Teapot
And the Teapot is left with the above ingredients in it for 5 minutes
Then you should have Brewed Tea

Scenario 3: Pouring the tea

Given a Teapot of Brewed Tea
And a Mug with some Milk in it**
When the Brewed Tea is poured in to the Mug
Then you should have a Perfect Cup of Tea

* “Do or do not. There is no should”
** Debatable. I think we need to triangulate this, or consult the client.

And after doing so, it appears there are two requirements:

1. Instructing firewall to forward ports
2. Allowing requests through firewall on the target computer

I am using a SpeedTouch 585 forwarding to a laptop running Windows 7.

It is also recommended of course that you have a static ip address.

How to instruct router to forward a port

TIP: Ensure you don’t have an ip address conflict (i.e., more than one computer on the same ip address) on your network, perhaps that confuses things for forwarding. Giving whatever machine you’re forwarding to a static ip address probably makes sense — you won’t need to change anything when that machine joins network then.

I have a SpeedTouch 585, and I did it through the web interface:

• Go to: “Home > Home Network > Devices > [device name]“
• Select “Configure” from the upper right part of the screen (between “Overview” and “Help”)
• From the “Connection Sharing” section, select “HTTP Server (World Wide Web)” from the list and press the “Add” button
• You’re now forwarding all HTTP requests to your public ip address on port 80 to your selected device on port 80.

There are full also instructions for port forwarding on a SpeedTouch 585.

TIP: You can telnet straight in to router on default port (23), bypassing the web UI.

TIP: Windows 7 has telnet disabled. Search for “turn Windows features on or off” to get the applet for enabling it.

Adding new firewall rules

Firewall rules are edited and applied through the “Game & Application Sharing” section.

For example. you may wish to host a website on port 99 on your laptop:

• Go to “Home > Toolbox > Game & Application Sharing”
• From the “Pick a task…” section, choose “Create a new game or application”
• From the “Clone Existing Game or Application” list, choose “HTTP Server (World Wide Web)”
• Check “Manual Entry of Port Maps”
• Press “Next”
• Enter 80 and 80 as the “Port Range”
• Enter 99 as the “Translate to”
• That’s it

Here’s the resultant mapping:

Protocol  Port Range	Translate To ...  Trigger Protocol  Trigger Port
Any	  80 - 80	99 - 99		  -		    -

TIP: You cannot edit anything in the “Home > Toolbox > Game & Application Sharing > Game or Application Definition” list if it is assigned to something (The edit link is missing). Unassign it before you edit it.

TIP: You have to explicitly enable logging for each “Game of Application” you attach to a device, otherwise you’ll get no logging at all.

What forwarding rules really look like

In the event logs, here’s what I get when I run a test with port 80:

FIREWALL rule (1 of 1) : Protocol: TCP
Src ip: 69.163.149.200
Src port: 47603
Dst ip: 192.168.1.65
Dst port: 99
Chain: forward_host_service
Rule Id: 2
Action: accept

Even though it does display an amber light instead of green, I think this is just a forwarding record, not a warning.

That stuff about the forward_host_service chain is available via telnet. Telnet in to your router and open the chains list.

Here are the chains I have:

Name                                             Description
-----------------------------------------------------------------
sink                                             system
forward                                          system
source                                           system
sink_fire                                        system
forward_fire                                     system
source_fire                                      system
forward_host_service                             system
forward_level                                    system
sink_system_service                              system
forward_multicast                                system
forward_level_BlockAll                           system
forward_level_Standard                           system
forward_level_Disabled                           system

Which includes forward_host_service, which contains these rules (including number 3):

:firewall rule list chain=forward_host_service format=cli

:firewall rule add chain=forward_host_service index=1
    name=_f_u_192.168.1.65:55768_55768
    dstip=_u_192.168.1.65
    serv=_u_17:55768_55768
    log=disabled
    state=enabled
    action=accept

:firewall rule add chain=forward_host_service index=2
    name=_f_sv_192.168.1.65:80_80
    dstip=_sv_192.168.1.65
    serv=_sv_6:99_99
    log=disabled
    state=enabled
    action=accept

:firewall rule add chain=forward_host_service index=3
    name=_f_sv_192.168.1.65:3128_3128
    dstip=_sv_192.168.1.65
    serv=_sv_6:3128_3128
    log=enabled
    state=enabled
    action=accept

How to allow connections through your firewall

Depends on your vendor obviously, but I am running ESET and I did this:

1. Setup > Personal firewall > Configure rules and zones…
2. Add new rule: TCP & UDP, port 80, All remote ports, All addresses

Coping with rejection

If you’ve gotten this far, then your router is forwarding as expected, but the test may still be failing. The next place to look then is on the machine being forwarded to.

Inspect the firewall logs on the target machine and you should have something like:

Packet blocked by active defense (IDS)
192.168.1.65:99
69.163.149.200:41791
TCP

So I had to add a new firewall rule.

If you have problems with your rules, put the firewall into interactive mode (this will prompt you to allow or deny all incoming requests), run the test, accept the connection and inspect the rule it generates.

TIP: Take care with the executable, try the rule with and without to see if it makes a difference.

How to test your router is open on a particular port

Try this utility.

Troubleshooting

Where are the SpeedTouch router log files?

Home > SpeedTouch > Event Logs

References

• Squid (Windows)
• You get signal (tests port forwarding)
• Illustrated instructions for configuring port forwarding in SpeedTouch 585

Filling out the form

Produces “Could not open socket” error in Chrome and Firefox.

Facebook Connect

On the register screen there is a Facebook Connect option, but this does nothing in Chrome, and does not appear at all in Internet Explorer.

Firefox does produce the window, so I select yes or whatever but then I can still not sign in.

Then I ask for my password to be sent, only to be told there is no account for my address.

Okay, then I think perhaps I don’t need to sign in to access the forum. I sign in to facebook and revisit: still can’t do anything but read posts.

In other news

Interestingly I do have punBB listed on my Application settings screen.

<bb />

to:

<bb>
    <mb />
</bb>

Many thanks and kind regards.