gregoryyoung

	public class the_inventory_changes_name {
	    public void Given() {
		    
		}

		public override void When() {
			
		}
		
		[Test]

gregoryyoung

When teaching in person classes testing is my favourite section to get into. The types of systems we have been discussing are both quite easy to test and they offer quite a few interesting opportunities that are not really feasible in many other types of systems.

One of these opportunities is that we can get documentation about our system being produced from our tests. This is a highly valuable thing to have on a project, these style tests are often called Executable Specifications. These tests are not only used for the purpose of validating the system but also for verifying that the system is ... doing the right thing which we will get more into later. So with that let's jump right into ... testing.

Testing is an important aspect of any system we build. I think every developer can agree that a failure caught early in our process is significantly less expensive than a failure caught late in the process or in production. Our goal is to fail fast.

So let's start by looking at an aggregate and how we might wr

gregoryyoung

#!/bin/bash
function f() {
	sleep "$1"
	echo "$1"
}
while [ -n "$1 ]
do
	f "$1" &
	shift
done

gregoryyoung

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace crap
{
    using System;
    using System.Collections.Generic;
    using System.Data;

gregoryyoung

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace crap
{
    using System;
    using System.Collections.Generic;
    using System.Data;

gregoryyoung

#Cheating

The patterns Copy-Replace, Stream-Split, and Join-Stream the last chapter are quite intense. Getting them to work on a running system is non-trivial. There will be times that they might need to be used however most of the time they can be avoided. 

The patterns will work in any scenario. It does not matter whether it is a system that is doing 5000 transactions per second with TB of data or one doing seconds per transaction with 1 GB of data. They work in the same way.

There exist however "cheats" that can be used to avoid the use of the more complicated patterns. Depending on the scenario they may or may not apply, the trade offs associated with them may be better or worse than the complexity associated with the other patterns. 

This chapter we will look at some of these "cheats" and where and when they might be applicable. Some are adding code complexity to avoid the need to versioning, others look at different deployment options. If possible you should generally prefer a pattern from this chap

gregoryyoung

using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Text;
using System.Threading;
using EventStore.ClientAPI;

namespace marketdata
{

gregoryyoung

Handlers

In Domain Driven Design, there are a series of small services that sit over the top of the domain. These services known as Application Services act as a facade over the the domain model. In CQRS based systems a similar pattern is used but it has been slightly refined. The refining of this pattern can be employed successfully in both systems that use CQRS and systems that stay using a single model for supporting reads and writes as many of the advantages come from simplicity of composition. To show Command Handlers, it is best to start with a typical Application Service and refactor our way to a Command Handler.

The Application Service

A stereotypical Application Service represents a given use case of the model. The Application Service itself generally does not directly implement the use case but instead coordinates objects from the domain to meet the requirements of the use case. This sounds like a small distinction but it is  a very important one, Application Services generally should not have "l

gregoryyoung

f(events) -> state
    match f(state, event) -> state

f(state, command) -> events

gregoryyoung

C:\Users\ack\src\AutoTestExtensions>"C:\Program Files\Red Gate\SmartAssembly 6\SmartAssembly.com" /build Obfuscation\Aut
oTest.VS.saproj
SmartAssembly v6.0.0.513
Copyright © Red Gate Software 2005-2011
Because I wanna ask you about your girlfriend. I must know who she is, or you would've told me her name.

System.NullReferenceException : Object reference not set to an instance of an object.