VSGuard
VSGuard is an implementation of relative debugging
for Microsoft's ® Visual Studio ® environment. VSGuard
builds on the rich environment provided by Visual Studio, and
adds relative debugging functionality seamlessly. Thus, users
already familiar with Visual Studio only need to learn a few new
commands and concepts to make full use of VSGuard.
Visual Studio allows users to manage two different projects concurrently
by building them into a Solution.
If you are porting from Visual Basic 6.0 to Visual Basic .NET,
VSGuard provides a Wizard that makes it very easy and quick to
build two different projects into one Solution. From this point,
VSGuard allows you to build assertions between data structures
in the two projects. It will run them concurrently, and compare
data automatically, reporting differences they occur.
Using this approach, you can test
whether a new project performs the same tasks as a previous version,
and if it doesn't, you can debug
it using VSGuard's powerful assertion mechanism. VSGuard builds
on the already powerful techniques used in other test tools,
but
allows you to trace errors down to an individual source line.
What's more, you don't need to capture large trace files, saving
both space and time.
Assertions between programs
Adding an assertion between projects is as simple as invoking
VSGuard. The control panel shown below appears. An assertion describes
locations in the two processes where the user assumes that key
data structures should be identical.
Once the dialogue box has appeared, you can add
assertions by:
- Right clicking on a variable in either project source file.
- Select Add To Assert on the pop up context menu.
This brings up a half filled Edit Assert form, as shown below.
The left hand side of the form (Target 1) now describes the
location at which you decided to create an assertion.
- Without closing the ‘Edit Assert’
window, perform the same ‘right click -> Add To Assert’
operation on same location within the other project. The other
half of the ‘Edit Assert’ window should fill with
information (if it doesn’t, then you may be performing
the right click on the same project twice). The ‘Edit Assert’
window is now filled with information describing the assertion
(see figure below).
Reporting differences
VSGuard reports differences as they are detected, avoiding the
need for confusing post mortem reports and logs. The following
screen shows that the variable "count" in two different
projects was the same on the first 12 iterations of a loop, and
then differed. At that point, VSGuard halted the execution and
allowed the user to locate the fault using normal Visual Studio
functionality. It couldn't be much easier!
How it works
Figure 1 shows a simplified schematic view of the architecture
of VSGuard under Microsoft's Visual Studio ® .NET. Visual
Studio .NET is build around a core ‘shell’ with functionality
being provided by commands that are implemented by a set of ‘packages’
These packages are conventional COM objects that are activated
as a result of user interaction (such as menu selection) within
Visual Studio .NET, and also when various asynchronous events
occur. This component architecture makes it possible to integrate
new functionality into the environment by loading additional packages.
Figure 1 – Guard Architecture
Figure 2 – Sample screen dump of VSGuard within Visual Studio
