Sunday, April 30, 2006



Simian is a simularity analyser. It looks at your code and finds similar code else where. Ideal to get a grip on cut and paste coders.

This is really a tool to deal with the problem that you should only code your program once. Just as with a database, only store your data in one place and don't duplicate the same approach should be taken to coding. This is the principle behind the 2nd normal form for a relational database.

I can think of one exception where Simian would give an incorrect result, and that is with code generation. Code generation is likely to produce lots of duplicate code, but it doesn't break the principle that you shouldn't duplicate code. The reason is that it is the compressed representation of the code, and the code generator itself that is important, not the output.

Well almost. If you do have lots of duplicate code, then you are going to have a larger program than necessary. Simian can help detect this, and you can then feed this back into your code generator, to optimise the output.

Friday, April 28, 2006


FxCop and Nunit

PMD has a set of JUnit rules. It would be interesting to implement them in FxCop


Code Analysis Tools

I am a heavy user of Fxcop. It is a code analysis tool that works on DotNet assemblies. That means it works with multiple languages, since it is operating at the compiled code level.

It is quite picky, but it is possible and worthwhile getting zero errors.

However, there are some errors that it cannot catch. These relate to information that is lost when you compile. I've come across two examples.

First is imports (or using). It is very easy to get extraneous imports. The compiler removes them, and so FxCop cannot tell if they exist in the source code.

Secondly relates to comments. There are great applications like NDoc. NDoc takes code, strips out XML comments and turns into documentation. Javadoc is another example. However, it is possible to change the code, and not keep the documentation up to date. For example, there is no check the signature of the function matches the signature in the documentation. FxCop like tools cannot check, because the comments are thrown away.

Interestingly tools for Java like IntelliJ handle this. You need to search through the code and find out exactly which imports are used, and could they be simplified.

Should be part of any good IDE.

Wednesday, April 26, 2006


The Problem with Unit Testing

One issue with unit tests is the limited number of paths through the software the tests test. Secondly, I'm not convinced that writing the test first, is the best way of writing code.

Taking each of these points in turn. You can address part of the limit number of paths by combining a code coverage tool with your unit tests. If you don't get code coverage, you can add more tests. However, what you really need is something that tests all the time.

Secondly, writing the test first focuses on a particular case, not on producing a good abstraction or good code. If you are not careful, the code is produced to meet a particular test case, not the set of test cases, or even the set of possible data.I've worked for a long time with Eiffel, and it has the interesting feature of design by contract. This combined with unit tests takes things to the next level. A lot of people who comment on DBC, have never used DBC in practice.

First, you change the way you program. It isn't write unit test first, it is contract first. Then write code / unit test. The change of emphasis is produce code that covers all cases. All cases are defined by the contract. Now it becomes clearer what the test cases are. You need to exercise the cases defined by the contract. Whether you write the tests, or the code first doesn't matter. Importantly, if you run the code with assertion checking on, you are testing the contracts as you go. Instead of testing just specific cases, you get universal testing. It is far more powerful.

There are some other alternatives that I can see coming in the future. FxCop and other static code analyzers are getting more sophisticated. Software such as the proposed NStatic are also interesting. Combining these with DBC would make something really powerful. I can also see the day when run time analysis during testing feeds back into the static analysis

Saturday, April 15, 2006



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