kontrawize

JUnit is not a unit test framework!

The most popular unit testing framework for Java is JUnit. It is based on the SUnit framework for SmallTalk, and has led to other "xUnit" frameworks like NUnit for C#. There are also some very worthwhile JUnit extensions, like DbUnit for databases, and XMLUnit and SUT (Schema Unit Test) for XML. All in all, it is an extremely successful piece of software. The only problem is the name. You see, JUnit really isn't a unit testing framework at all.

JUnit is a testing framework, a really useful testing framework. So useful, in fact, that I am happy to use it (in combination with Apache Ant or Maven) for testing non-Java code, like XSLT. I highly recommend JUnit as a testing framework - but that doesn't make it a unit testing framework.

So, what is a unit test? Well, that begs the question of "what is a unit?" A unit is a small, self-contained piece of code that you can test independently. In object-oriented programming languages like Java, most people consider a class to be the right choice for a unit - it's typically something small that should make sense in its own right. JUnit is certainly a good way to write tests for testing an individual class. So why isn't it a unit test framework?

The issue is this. Suppose you are testing class A, and class A calls methods from classes B, C, and D. If you write tests for class A using JUnit, then you will also be calling code in classes B, C, and D, so you aren't just testing class A in isolation. You won't be able to get a 100% test pass rate for class A if there are bugs in the code for classes B, C, and D. When class A is a high-level class in an application, one that calls most of the other classes in the application, that means you aren't able to independently write and debug A until all of the other classes in the application are written and working, and that is the kind of dependency that unit testing, in the classical sense, is meant to avoid.

If JUnit were a unit testing framework, it would help you write unit tests specifically. It would help you avoid actually calling the code in classes B, C, and D. It doesn't do that (although you can always try other tools like MockObjects and EasyMock to help with that).

In truth, most people don't do real unit testing, because mocking out of classes (like B, C, and D) can be more expensive that just calling out to those classes. So while JUnit is widely used, it is widely used for non-unit testing. That isn't a bad thing, it simply is as it is. The only problems are:

• people using JUnit sometimes think they are doing unit testing, when they aren't;
• people sometimes don't think of JUnit as the right testing framework to use for non-unit testing, even though that is what it is mostly used for.

What's in a name, I guess. Great tool, just needs a better name. Not that I can think of one, though.

[ Technorati tags: Java ]

StarOffice 8 & Linux

After my quick test of StarOffice 8 under Windows XP, I installed it today under SUSE Linux 9.3 Pro. No problems at all; I took the brave step of removing all other StarOffice versions before installing, but there was nothing to worry about, I had no problems opening legacy documents.

The word processor and spreadsheet look pretty similar to before, but the Impress appliction (equivalent to PowerPoint in MS Office) has a much improved interface. Whenever I do slideware, I use Impress, so I appreciate the improvements.

So, no interesting stories about installing StarOffice 8, but I tell you, I'm grateful sometimes to have nothing exciting to say.

Object to an Overabundance of Objects

Today I read this great post from Slobodan Celenkovic on how easy it is to chew up memory in your Java application by creating more objects than you really need. This is based on hard figures from an application he was running, not just on theory. The same issues almost certainly apply to C#, Python, etc. too.

It's easy to get into bad habits on small projects, and then suddenly find that your approach just doesn't scale up for big projects. When that happens, it's a good idea and follow Slobodan's example - investigate and understand, don't just try hacking code and hoping.

[ Technorati tags: Java, software architecture ]

StarOffice 8 quick test

Since yesterday's post, I've downloaded the demo versions of StarOffice 8 for Windows & Linux. First up I tried Windows (since I do my important stuff under Linux, so I have to be more cautious there).

First impressions are good! Opening various legacy StarOffice 7 and MS Office documents, all looked fine, none of the font problems that the beta version had. The delay in releasing StarOffice 8 looks to have been put to good use.

StarOffice 8 available

StarOffice 8 is finally available! Close cousin to OpenOffice 2, I've been using StarOffice for some years now, and the beta of version 8 looked good. Mind you, the beta also had some real problems in reading legacy StarOffice and MS Office documents, so I will be looking really closely at how the release version goes.

I'll follow this up when I manage to get myself a copy.

Giant Squid

Wow! The first pictures of a live giant squid have been taken! See this National Geographic article for the details. Cool.

SVG and Opera, part 2

I noted that Opera 8.5 does not display text in SVG figures. The (quick) reply from Opera support came today - Opera supports only SVG Tiny, not the whole of SVG. It's a pity I couldn't find this information in their support site when I searched for "SVG", but at least I know now.

SVG MIME type

Apologies that the compressed SVG files (.svgz) from my post yesterday don't download and display correctly. It seems to be that the TypePad server(s) aren't configured with the MIME type (image/svg+xml). I've logged a ticket for TypePad to look at the issue; hopefully it can be resolved. In the meantime, if you want to look at them, it should be possible to save them and then open the local saved files.

SVG and Opera

For my XML 2005 conference paper, I decided to do SVG diagrams for the first time. I used the beta of StarOffice 8 (close cousin of OpenOffice 2) to do the figures and export them as SVG, and it did a good job. I'm not an artist, not at all, so don't expect much, but I thought they turned out well for the short amount of time they took me to create:

• repository-organisation.svgz
• updated-organisation.svgz

Now, both diagrams contain some text. However, when I viewed them in Opera 8.5, the text was gone! A quick check with IE6 (with the Adobe SVG plug-in) and with the Inkscape SVG editor showed that the text was in the SVG. So it's an Opera problem.

Luckily, as a purchaser of Opera, I have access to the premium support service, so I've logged the issue. Hopefully it won't be too long before they can deliver a fix. Text aside, SVG looks great in Opera without any need for a plug-in, so I'm sure they won't have any trouble with this issue.

XML 2005 paper

I finished and submitted my XML 2005 conference paper yesterday. It's always a relief to get that done. What I've submitted is the paper for the conference proceedings; I still need to do the slides for the actual presentation. The topic is "Creating and Maintaining Large Families of Related Schemas". Most of my talks tend to be "how we should be doing this" pieces, but this one is a "how I actually did it in practice" piece. That means it doesn't have a single golden thread of intellectual purity tying it together, rather it is a collection of a whole variety of things that I needed to do to build and manage a family of >450 W3C XML Schemas for a client.

If you can make it to Atlanta in November for XML 2005, it should be a lot of fun (the previous conferences certainly have been). If you would like to catch up with me at the conference, let me know, and we can organise something. It's always nice to put faces to names and/or e-mail addresses.