Any software product being developed has to go through the testing phase. In this phase, testers detect any kinds of defects present within the software and report it to the developers so that they can fix it.
But, what are the main causes of these defects in a software system? Given below are a few important reasons due to which the defects may arise in any software system.
The user, who is actually using the software application or product may not have enough knowledge about the product to use it properly
There is a possibility that the software is not being used as it should be, which in turn leads to defects or failures within the system
Maybe the developers may have made mistakes while writing the code, because of which the defects may have introduced within the system design or architecture
Defects and failures also arise due to the incorrect setup of the testing environments
Let us take an example to understand the presence of defects and failures in a software system better. Consider the diagram given below –
In the above figure, we can see that there are four products built according the four requirement specifications given. Here, you can see that the product built in the Requirement 1 has no errors or mistakes in any of the development phases. The project requirements are gathered correctly, the product is designed to meet the requirements and is built to meet the design requirements. Hence, the end product developed works as expected with correct functional and non-functional attributes.
Now going through the Requirement 2, the product build through this process has correctable defects. That is because during the software development process, the project specification requirements were gathered correctly and the design was created to meet these requirements.
However, there were mistakes done in building phase and hence the product developed has defects. These defects are easy to correct since the mistakes were done only in the building process.
Considering the product built in Requirement 3 now, you can see that the product developed has issues in its design, leading to possible defects and failures. In this case, the project specification requirements were gathered correctly, but errors were made during the designing process.
Then, the product was built to meet the design specifications and so the end product has design flaws, which needs to be corrected before the final launch. The defects in this case are a bit difficult to fix, since mistakes were done the designing phase, which is an early stage in software development lifecycle.
Finally, taking into consideration, the product built according to the Requirement 4. In this case, the errors were made in specifying the project requirements itself. These defects can be minor or major, depending on how big the mistake is. If a major product requirement is misunderstood, then it is possible that the product built is completely different from what end users expected. Once these defects in requirement phase are fixed, only then the product can be finally launched in the market.