If you happen to be working in the IT industry, I can bet that you would have come across the word 'Defect' (or other popularly used word 'Bug') almost on daily basis. A 'defect' is nothing but a case of something not working as expected.
You can see defects usually in all walks of life. There are defects in the house you live, bus you take, car you drive, laptop you use. You would have seen various manufacturers recalling their products because they want to fix a defect.
Why one should worry about defects? Because defects are usually costly. Each defect has a cost associated to it. Cost of each defect depends upon which phase it got introduced and which phase it got caught. A defect that was introduced in design phase and caught in deployment phase will be the most costly defect. In the worst case, a defect could be life threatening. For example, a small defect brought down the space shuttle Columbia where all the astronauts were killed.
The big question is why and how defects get introduced?
In any product development, there are various stages. Let us take an example of software product as I am more familiar with this. We can divide the software product development in various stages like requirement collection, high level design, low level design, user-interface design, implementation, testing, deployment etc.. Defects get introduced in almost every stage.
Someone may ask, how come defects gets introduced in the testing phase. Actually testing is suppose to figure out all defects but as we know by experience that it is not the case. So this means that there is some defect in our testing because of which we are not able to detect all defects.
When you designs your product, it is almost impossible to test the design for all possible inputs. So there will always be some inputs for which you cannot test your design or implementation. So theoretically, there is a possibility that your design may fail for some such input. If I extend the above, we can safely say that in theory, it is almost impossible to avoid defects. Similarly, a developer without required level of skills, implementing the desgin will introduce more defects.
In my opinion, as mentioned above, in a completely new software, defects are introduced in all the stages. Once defects are seen, they are fixed. This is when more defects are introduced in the software. So this becomes a unavoidable cycle.
Why defects are introduced when fixing a defect? There could be various reasons like the developer does not know the big picture or there is not enough documentation about the implementation or there is no review process or the developer's skills are not good enough. In my opinion, review process can help in most of these cases. For example: even if the developer fixing the defect does not know the big picture, the chances of getting defects can be reduced if an expert review the fix. In one of my earlier post, I had talked about the necessity of code review. In that post, I argued in favour of code review which helps in reducing the defects in the system.
So defects are costly and seems unavoidable but there are means and processes with which we can reduce the occurrence of defects. I am a big supporter of review process. In my opinion, number of defects in the system can be reduced if there are reviews in each stage of development. Also, I think there must be more focus on better reviews in the preliminary stages like design. What do you think about this? It would be great if you can share the particular mean or process that has really helped you in reducing defects.
You can see defects usually in all walks of life. There are defects in the house you live, bus you take, car you drive, laptop you use. You would have seen various manufacturers recalling their products because they want to fix a defect.
Why one should worry about defects? Because defects are usually costly. Each defect has a cost associated to it. Cost of each defect depends upon which phase it got introduced and which phase it got caught. A defect that was introduced in design phase and caught in deployment phase will be the most costly defect. In the worst case, a defect could be life threatening. For example, a small defect brought down the space shuttle Columbia where all the astronauts were killed.
The big question is why and how defects get introduced?
In any product development, there are various stages. Let us take an example of software product as I am more familiar with this. We can divide the software product development in various stages like requirement collection, high level design, low level design, user-interface design, implementation, testing, deployment etc.. Defects get introduced in almost every stage.
Someone may ask, how come defects gets introduced in the testing phase. Actually testing is suppose to figure out all defects but as we know by experience that it is not the case. So this means that there is some defect in our testing because of which we are not able to detect all defects.
When you designs your product, it is almost impossible to test the design for all possible inputs. So there will always be some inputs for which you cannot test your design or implementation. So theoretically, there is a possibility that your design may fail for some such input. If I extend the above, we can safely say that in theory, it is almost impossible to avoid defects. Similarly, a developer without required level of skills, implementing the desgin will introduce more defects.
In my opinion, as mentioned above, in a completely new software, defects are introduced in all the stages. Once defects are seen, they are fixed. This is when more defects are introduced in the software. So this becomes a unavoidable cycle.
Why defects are introduced when fixing a defect? There could be various reasons like the developer does not know the big picture or there is not enough documentation about the implementation or there is no review process or the developer's skills are not good enough. In my opinion, review process can help in most of these cases. For example: even if the developer fixing the defect does not know the big picture, the chances of getting defects can be reduced if an expert review the fix. In one of my earlier post, I had talked about the necessity of code review. In that post, I argued in favour of code review which helps in reducing the defects in the system.
So defects are costly and seems unavoidable but there are means and processes with which we can reduce the occurrence of defects. I am a big supporter of review process. In my opinion, number of defects in the system can be reduced if there are reviews in each stage of development. Also, I think there must be more focus on better reviews in the preliminary stages like design. What do you think about this? It would be great if you can share the particular mean or process that has really helped you in reducing defects.
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