In electronics engineering, a fault simulator predicts what will happen to a circuit when a component malfunctions, without having to actually install a bad component in the circuit. DPFS (DevPartner Fault Simulator) applies a similar idea to software: It shows you what will happen to your .Net application when an abnormal situation occurs, without having to actually create the situation.

The Bottom Line Compuware DevPartner Fault Simulator 2.0 Compuware, compuware.com Good  7.4 criteria score weight Capability 7 30% Integration 8 20% Ease-of-use 8 15% Performance 8 15% Documentation 6 10% Value 7 10% Cost: $1,000 per named user, $3,000 per concurrent user; upgrades are $450 per named user and $1,350 per concurrent user Platforms: Windows 2003 Server, XP, Vista; .Net Framework 1.1 and 2.0; integrates with Visual Studio 2005, Visual Studio .Net 2003 Bottom Line: DPFS 2.0 is a useful tool for testing and improving .Net applications’ exception handling, and can be a time-saver for serious .Net shops. The price is still high, but this version has some improved capabilities and better integration with code coverage and defect tracking tools than its predecessor. About our Reviews and Scoring Methodology

Fault Simulator 1.0 arrived in 2005, to mixed reviews. InfoWorld’s previous review praised the concept but raised questions about the utility of the implementation. The biggest concerns were DPFS 1.0’s lack of integration with other Compuware tools, and its inability to affect classic C++ exception handling.

DPFS 2.0 still does not simulate faults for classic native C++ exception handling, although it does simulate faults for managed C++. It also now integrates with Compuware’s Coverage Analysis tool and has a number of other improvements that will make .Net developers’ and testers’ lives easier. However, there’s room for growth -- the feature set and documentation still have some rough spots.

Fault-Finding Mission

DPFS 1.0 showed developers where it could simulate .Net faults by displaying curly underlines in Microsoft Visual Studio. The underlines appeared beneath lines of code calling .Net functions that DPFS recognized as ones that throw exceptions.

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DPFS 2.0 improves on that display, posting an icon to the right of each line of code with a possible exception, and another icon at the end of each method that can throw exceptions. If you click on the icon at a line end, you can add simulated .Net faults for the methods called as well as add surrounding try/catch blocks for any or all of the possible faults. This advances DPFS from merely simulating faults to also generating some of the code to handle the faults.

Click on the icon at the end of a method, and you can add XML documentation comments for the possible exceptions to the method, indicating that you want to allow exceptions to be caught by callers of the method. Once you’ve built the application, the new XML comments can be read by DPFS and used to create simulated faults for the methods they document.

I think the try/catch block generation is a major productivity boost for a developer trying to make an application more robust. DPFS doesn’t actually write the body of the catch clauses, just the block skeleton; you still have to think about what action is appropriate to handle each fault.