Software Testing Fundamentals
let's start by considering why testing is needed. Testing is necessary because we all make mistakes. Some of those mistakes are unimportant, but some of them are expensive or dangerous. We need to check everything and anything we produce because things can always go wrong - humans make mistakes all the time - it is what we do best! Because we should assume our work contains mistakes, we all need to check our own work. However, some mistakes come from bad assumptions and blind spots, so we might make the same mistakes when we check our own work as we made when we did it. So we may not notice the flaws in what we have done. Ideally, we should get someone else to check our work - another person is more likely to spot the flaws.Here, we'll explore the implications of these two simple paragraphs again and again. Does it matter if there are mistakes in what we do? Does it matter if we don't find some of those flaws? We know that in ordinary life, some of our mistakes do not matter, and some are very important. It is the same with software systems. We need to know whether a particular error is likely to cause problems. To help us think about this, we need to consider the context within which we use different software systems
Software systems context
These days, almost everyone is aware of software systems. We encounter them in our homes, at work, while shopping, and because of mass-communication systems. More and more, they are part of our lives. We use software in day-today business applications such as banking and in consumer products such as cars and washing machines. However, most people have had an experience with software that did not work as expected: an error on a bill, a delay when waiting for a credit card to process and a website that did not load correctly are common examples of problems that may happen because of software problems.Not all software systems carry the same level of risk and not all problems have the same impact when they occur. A risk is something that has not happened yet and it may never happen; it is a potential problem. We are concerned about these potential problems because, if one of them did happen, we'd feel a negative impact. When we discuss risks, we need to consider how likely it is that the problem would occur and the impact if it happens. For example, whenever we cross the road, there is some risk that we'll be injured by a car. The likelihood depends on factors such as how much traffic is on the road, whether there is a safe crossing place, how well we can see, and how fast we can cross. The impact depends on how fast the car is going, whether we are wearing protective gear, our age and our health. The risk for a particular person can be worked out and therefore the best road-crossing strategy.
Causes of software defects
Why is it that software systems sometimes don't work correctly? We know that people make mistakes - we are fallible.If someone makes an error or mistake in using the software, this may lead directly to a problem - the software is used incorrectly and so does not behave as we expected. However, people also design and build the software and they can make mistakes during the design and build. These mistakes mean that there are flaws in the software itself. These are called defects or sometimes bugs or faults. Remember, the software is not just the code; check the definition of software again to remind yourself. When the software code has been built, it is executed and then any defects may cause the system to fail to do what it should do (or do something it shouldn't), causing a failure. Not all defects result in failures; some stay dormant in the code and we may never notice them.
let's start by considering why testing is needed. Testing is necessary because we all make mistakes. Some of those mistakes are unimportant, but some of them are expensive or dangerous. We need to check everything and anything we produce because things can always go wrong - humans make mistakes all the time - it is what we do best! Because we should assume our work contains mistakes, we all need to check our own work. However, some mistakes come from bad assumptions and blind spots, so we might make the same mistakes when we check our own work as we made when we did it. So we may not notice the flaws in what we have done. Ideally, we should get someone else to check our work - another person is more likely to spot the flaws.Here, we'll explore the implications of these two simple paragraphs again and again. Does it matter if there are mistakes in what we do? Does it matter if we don't find some of those flaws? We know that in ordinary life, some of our mistakes do not matter, and some are very important. It is the same with software systems. We need to know whether a particular error is likely to cause problems. To help us think about this, we need to consider the context within which we use different software systems
Software systems context
These days, almost everyone is aware of software systems. We encounter them in our homes, at work, while shopping, and because of mass-communication systems. More and more, they are part of our lives. We use software in day-today business applications such as banking and in consumer products such as cars and washing machines. However, most people have had an experience with software that did not work as expected: an error on a bill, a delay when waiting for a credit card to process and a website that did not load correctly are common examples of problems that may happen because of software problems.Not all software systems carry the same level of risk and not all problems have the same impact when they occur. A risk is something that has not happened yet and it may never happen; it is a potential problem. We are concerned about these potential problems because, if one of them did happen, we'd feel a negative impact. When we discuss risks, we need to consider how likely it is that the problem would occur and the impact if it happens. For example, whenever we cross the road, there is some risk that we'll be injured by a car. The likelihood depends on factors such as how much traffic is on the road, whether there is a safe crossing place, how well we can see, and how fast we can cross. The impact depends on how fast the car is going, whether we are wearing protective gear, our age and our health. The risk for a particular person can be worked out and therefore the best road-crossing strategy.
Causes of software defects
Why is it that software systems sometimes don't work correctly? We know that people make mistakes - we are fallible.If someone makes an error or mistake in using the software, this may lead directly to a problem - the software is used incorrectly and so does not behave as we expected. However, people also design and build the software and they can make mistakes during the design and build. These mistakes mean that there are flaws in the software itself. These are called defects or sometimes bugs or faults. Remember, the software is not just the code; check the definition of software again to remind yourself. When the software code has been built, it is executed and then any defects may cause the system to fail to do what it should do (or do something it shouldn't), causing a failure. Not all defects result in failures; some stay dormant in the code and we may never notice them.
very useful dude....thanks..
ReplyDeletevery useful dude....thanks..
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