Code and Unit Testing

Last time I talked about Unit Testing or external types of test. Now some thoughts on internal testing.

IDEs (Integrated Development Environments) using basic debugging techniques (i.e. single step, view variables, break points, etc) are the front line of internal testing. They give developers insight in to what's going on in a program. A program is run, it doesn't work, you debug. But there are other ways, more powerful ways, of doing debugging internal to a module that aren't as time consuming.

First, there is an ASSERT statement in most C/C++ languages. In NI's CVI in the toolbox it is a DoAssert statement (include toolbox.h to use this). The DoAssert statement is used to help find problems during development that don't happen that often. Basically, it is a condition passed to the DoAssert (Eample: i>1) and if the condition evaluates to TRUE, execution continues. If the statement evaluates to FALSE, module information is printed and execution stops. It prints out the module name a number like the line number (remember __LINE__ is the current line number in the program) and a message, typically with some debug information.

I use ASSERT or DoAssert (CVI) to check for out of tolerance conditions that happen once in a blue moon (good 'ol southern saying that means “not very often”).

Another way of internal testing is to do logging. Some people only use logging as a last resort after problems are found but I advocate putting in logging as your coding, putting log statements in at potential problem spots. Compiler directives can control whether the logging is executed or not. (#ifdef and #endif)

I have some logging routines laying around that I always use. They use the vaprintf style of functions so the logging is more like a printf statement in C. The LogOpen function is called at the start that opens the log file. A LogClose function is called at the end to stop the logging. It does I/O during execution by flushing the buffer every time the LogData is called but that can be controlled with compiler directives. The flush can be turned off if you don't want the I/O delays.

And, like I started with, there is always the standard debugging tools. These are just a couple of ways to do debugging internal to the module. I just want people to step out of their little box and think “How can I make my code better?” and “What can I do to keep from giving incorrect results or give errors?”