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consider a [scenario] where you are moving a file from folder a

To Folder B

Think of all the possible ways [you] can test this

Pause the tutorial and think over the exercise

Apart from the usUal scenarios, you can also test the following conditions

Trying to move the file when it is open you [do] not have the security rights to paste the file in Folder B

Folder B. Is on a shared [drive] and storage capacity is full

Folder B. Already has a file with the same name in fact the list is endless or

Suppose you have 15 input fields to test each [having] 5 possible values

The number of combinations to be tested would be 5 raised to 15

If you were to test all the possible combinations

Project execution time and costs will rise exponentially

Hence one of the testing principles states that exhaustive testing is not possible

instead we need the optimal amount of testing based on the risk assessment of the application and the million dollar question is

How do you determine this risk?

To answer this let's do an exercise in your opinion, which operation is most likely to cause your operating system to fail

I'm

Sure most of you would have guessed opening 10 heavy graphics applications all at the same time

So if you were testing this operating system

You would realize that defects are likely to be found in a multitasking module and that needs to [be] tested thoroughly

Which brings us to [our] next principal defect?

clustering which states that a small number of modules contain most of the defects detected

With experience you can identify such Risky modules

but this approach has its own problems if

The same tests are repeated over and over again

Eventually the same test cases will no longer find new bugs. This is another principle of testing called

Pesticide Paradox to overcome this the test cases need to be regularly reviewed and revised

Adding new and different test cases to help find more defects

But even after all this sweat and hard work and testing you can never claim your product is bug free to drive home this point

Let's see this video of the public launch of Windows 98

Let's plug it in its going to say hey

I see you put in a new device and it's going to load in the appropriate drivers you'll notice that this scanner build

whoa

moving right along

Must be why we're not shipping Windows 98

You would think a company like Microsoft would have tested their os

Thoroughly and would not risk their reputation just to see their os crashing during its public launch

Hence the testing principle states that testing shows the presence of defects

testing reduces the probability of undiscovered defects remaining in the software

But even if no defects are found it is not [a] proof of correctness or a proof that no defects remain in the system

But what if you work extra hard taking all precautions and making sure your software product is

99% bug free and the software does not meet the needs and requirements of the client

Which leads us to [our] next principle which states that absence of error is a fallacy

finding and fixing defects does not help if the system build is unusable and does not fulfill the users needs and

requirements [to] fix this problem the next principle of testing

Early testing states that testing should start as early as possible in the software development [lifecycle]

So that any defects in the requirements or design phase are captured as well

we'll have more on this principle [in] a later tutorial and

The last principle of testing states that the testing is

Context dependent which basically means that the way you test an e-Commerce site will be different from the way you test a commercial off-the-shelf

Application before we close this tutorial. Here's a quick recap of the seven testing principles