Important steps in the modern software development process are the steps of testing and debugging software to ensure that the software will work and function as expected in its intended processing environment. These steps are usually implemented as methodical processes of finding and reducing the number of defects in the software program to make it behave as expected or intended.
These tasks are often made much more difficult if the software program is tightly coupled to other devices, subsystems, or programs because it is often difficult to determine and test the complex interactions between the software and the other subsystems and components in the overall system, particularly if the operating environment is constantly subject to multiple inputs and status changes. Moreover, changes in one part of the system may cause unexpected results and errors to emerge in other parts the system.
For example, programmers often have a problem testing software that runs in the context of an operating system because of the enormous number of complex inputs and interactions that occur on a near constant basis. One reason for this is because, when errors occur, it is very difficult to repeatedly observe the errors and to repeat the error in a deterministic way. This desire to be able to repeatedly observe the errors is very important for purposes of performing program debugging and correction.
A common example of a program that may need to be tested in the context of an operating system is a device driver that executes in the context of an operating system (such as the Linux operating system). A typical type of problem that occurs with device drivers is the intermittent problem that is experienced when the timing of events cause a problem, e.g., when a particular state S1 of the hardware combines with a particular state S2 of the device driver software such that an error occurs, where neither the state S1 of the hardware nor the state S2 of the software by themselves would cause an error but it is the combination of both states occurring at exactly the same time that causes the error.
In this situation, it is a common struggle for software engineers to attempt to observe such intermittent problems, and it is particularly difficult for the engineers to reproduce such problems so that they can be debugged. Since the problems are often timing related, typical debugging techniques such as using print statements or using a software debugger introduces changes to the system states which could change the system timing and mask the problem.