SMOKE  TESTING or SANITY TESTING  or BUILD VERIFICATION TESTING 

Testing the basic or critical features of an application before doing thorough testing or rigorous testing is called as smoke testing.

It is also called Build Verification Testing – because we check whether the build is broken or not.

Whenever a new build comes in, we always start with smoke testing, because for every new build – there might be some changes which might have broken a major feature ( fixing the bug or adding a new feature could have affected a major portion of the original software).

In smoke testing, we do only positive testing – i.e, we enter only valid data and not invalid data.

Do we have separate testing (or) do we have to do it in between FT, IT, ST ? Then, where actually do we do smoke testing? Observe

From the above diagram, it may be confusing when we actually do smoke testing

Now, we have to understand that smoke testing is done in all testing before proceeding deep into the testing we do.

The below example will make us understand better when to do smoke testing,

Developers develop application and gives it for testing. The testing team will start with FT. suppose we assume that 5 days we are given for FT. on the 1^st day, we check one module and later 2^nd day we go for another module. On the 5^th day, we find a critical bug, when it is given to the developer – he says it will take another 3 days to fix it. Then we have to stretch the release date to extra 3 days.

Then how do we overcome this ? – Observe how smoke testing works here. In the above scenario, instead of testing module by module deeply and come up with critical bug at the end, it is better to do smoke testing before we go for deep testing i.e,

 in each module – we have to test for basic (or) critical feature and then proceed for deep testing. The scenario will be like this as shown in the figure below,

Question arises – how do we know which is the critical feature? – we will come to know which is the critical feature or basic feature when we proceed with the testing.