Feeds

Designing software for testability

You know it makes sense

Choosing a cloud hosting partner with confidence

The subject of testing seems to be in the air at the moment - Matt Stephens recently discussed it in his "Agile" column entitled "Don't unit test GUIs". This month in the Java column we are also going to look at testing, but this time from the viewpoint of design.

Software design, in some ways, is a particularly strange art. The design itself is not a physical thing, it is not the artefact that will eventually be run nor is it any more concrete (in the sense of the real world) than the actual software that will be executed. Yet it is key to the successful production of effective software. It is also the step that will determine the overall structure, nature, and approach of the resulting software. Herein, of course, lies one of the ironies of the software development world – you can't test a design (at least not directly).

However, this does not mean that testing isn't relevant for design activities. Indeed, I would argue that testing is as important a consideration during design as it is during coding. It is certainly no less important than any other requirement that needs to be considered during any design steps.

In this column I am going to present two aspects to the consideration of testing that need to be considered during any design process. These are "design for testability" and "test first design".

Design for testability

Given any set of requirements, different designers may come out with markedly different designs. These designs will then form the blueprint of the way in which the software will be built, deployed, and executed. It is not necessarily true that one design is better per se than another, but it may certainly be true that one design is easier to implement, maintain, deploy and test than another. It is this last point that I want to consider here. That is: "How easy is a design to test once implemented in a language such as Java?"

It is certainly possible to design software in such a way as to make testing easier. The easier software is to test, the more likely it is to be tested. Certainly, in my experience, if software is hard to configure, set up and to actually test then less testing gets done. If software is easier to test more testing is likely to be performed and a greater number of flaws may be discovered.

As an example, consider the Java application presented below. As can be seen from this diagram we have a simple stateful session bean (using EJB 2.0) that provides a calculator-like function. However, to test the "business logic" of this bean we will need to either compile the classes, create appropriate XML files, jar these up with the classes, and deploy to an EJB container such as JBOSS or possibly OpenEJB (which can provide a lightweight test environment). We will then need to create a client class that uses an initial context and an EJB Home object to access the remote bean object. Only then can we test the business logic.


Figure 1: Standard stateless EJB design

However, we may all put off testing the business logic because we do not have a tool such as JBOSS or OpenEJB installed – and certainly the mantra of "test often and little" might well be forgotten.

Business security measures using SSL

Next page: Test first design

More from The Register

next story
'Windows 9' LEAK: Microsoft's playing catchup with Linux
Multiple desktops and live tiles in restored Start button star in new vids
Not appy with your Chromebook? Well now it can run Android apps
Google offers beta of tricky OS-inside-OS tech
New 'Cosmos' browser surfs the net by TXT alone
No data plan? No WiFi? No worries ... except sluggish download speed
Greater dev access to iOS 8 will put us AT RISK from HACKERS
Knocking holes in Apple's walled garden could backfire, says securo-chap
NHS grows a NoSQL backbone and rips out its Oracle Spine
Open source? In the government? Ha ha! What, wait ...?
Google extends app refund window to two hours
You now have 120 minutes to finish that game instead of 15
Intel: Hey, enterprises, drop everything and DO HADOOP
Big Data analytics projected to run on more servers than any other app
prev story

Whitepapers

Providing a secure and efficient Helpdesk
A single remote control platform for user support is be key to providing an efficient helpdesk. Retain full control over the way in which screen and keystroke data is transmitted.
Saudi Petroleum chooses Tegile storage solution
A storage solution that addresses company growth and performance for business-critical applications of caseware archive and search along with other key operational systems.
Security and trust: The backbone of doing business over the internet
Explores the current state of website security and the contributions Symantec is making to help organizations protect critical data and build trust with customers.
Reg Reader Research: SaaS based Email and Office Productivity Tools
Read this Reg reader report which provides advice and guidance for SMBs towards the use of SaaS based email and Office productivity tools.
Security for virtualized datacentres
Legacy security solutions are inefficient due to the architectural differences between physical and virtual environments.