A. Priority and severity of bugs

Priority of a bug can be defined as the order in which the bug must be fixed in order to let the system run smoothly. Priority tells the time bound in which the bug must be resolved or fixed depending on its severity that it has  on the system.

Priority can be:

1. Low
2. Medium
3. High

Severity is defined as the impact that a bug creates one the system i.e, to what extent the bug affects the systems functionality, performance or stability based on the bug-type.

Higher the severity of a bug, the higher must be the bug’s priority

Severity can be:

1. Critical
2. Major
3. Moderate
4. Minor
5. Cosmetic

If a bug is affecting a software to a great extent or on a great level i.e, the bug is of high severity then the bug must be fixed as soon as possible since the bug is of higher priority.

B. Boundary Value analysis

In boundary value analysis the tester checks for the boundary values and checks the result on these boundaries.

A tester divides data into partitions and each partition has its own values of the boundary for which the tester tests the input for expected output. In boundary values analysis the given data is divided into partitions where each partition has its own boundary.

Suppose the tester checks values between 5 to 9 for a particular application functionality so the data is divided into following partitions:

---------------       -----------------      ---------------      ---------------
       0              |  5           9|       |10       99 |      | 100               
---------------       -----------------      ---------------      ---------------
Partition-1              partition-2          Partition-3           Partition-4

{invalid}               {  valid  }            {  invalid  }        { invalid }  

In boundary value analysis, the tester checks only for boundary values of each partition which are:  0,5,9,10,99,100.

**In boundary value analysis we check both valid and invalid boundaries**

C. Equivalence Partitioning 

In Equivalence partitioning, A tester divides data into equal partitions and tester derives test cases for each partition and this reduces the time in which testing takes place because of less number of test cases since data is divided into partitions. Each partition has its own values of the boundary for which the tester tests the input for expected output. In boundary values analysis the given data is divided into partitions where each partition has its own boundary.

---------------       ------------------     ----------------      ---------------
        0             |  5          9 |      | 10         99 |      | 100               
---------------       -----------------      -----------------     ----------------
Partition-1          partition-2               Partition-3           Partition-4

{invalid}            {  valid  }               {  invalid  }         { invalid }

D. Pesticide Paradox

Pesticide paradox principle states that “ If you uses the same test cases over and over again in a period of time interval so these test cases are not capable of finding the new defects in the system”

To find the new defects or bugs in a system, the tester must use different strategies or execute different test cases in different intervals of time.

In order to find the new defects or bugs in a system, new strategies must be followed in different time intervals. Also, the test cases must be regularly revised and new test cases should be introduced in the system.
 

E. why and when smoke testing is used?

Why? 
smoke testing is carried out when the tester needs to check whether a software product is stable or not i.e, all the functionality are working as per the needs or not.

When?
Smoke testing is carried out in the early phase so smoke testing does not require much planning. After smoke testing, the testing team approves the software product for further testing.
 

F. Why and when unit testing is used?

Why?
A Software is divided into units and each unit is tested separately in unit testing so unit testing is carried out to find and fix the bugs in the early stage of development.

When?
Unit testing is done on each unit of the software that is being developed so unit testing is carried out in the early phase of development of a software.
 

G. Why and when integration testing is used?

Why?
Integration Testing is performed to check whether the integrated units affect the functionality of the whole software or not.

When?
Once the software is developed into units and each unit is tested  individually, those units are integrated and then integration testing is    performed on those integrated units.
         

H. Why and when System testing is used?

Why?
The system testing is performed to check the functionality of the system as a whole. System testing checks the system as a whole to validate the functionality  of the whole software product.

When?
System testing is performed when all the units are integrated into one system as a whole.

I. Why and when Acceptance testing is used?

Why?
Acceptance testing/user acceptance testing  is carried out to check the software functionality and user/customer satisfaction from the customer's end. Sometimes, the client hires a tester at the client side to perform testing on the client’s behalf at the client end, then this testing is known as Beta Testing.

When?
 Acceptance testing is performed when the software is deployed at the end user site after the final software product is bug free and passed by the testing team.

J. Why and when regression testing is used?

Why?
Whenever a new module is added to a software for any reason, say for the addition of one more functionality to a software. Regression testing checks whether the added module affects the functionality, normal data-flow of the whole software or not.

When?
Regression testing is a type of testing that is performed when a new module is added to a software.

K. Which testers come under black-box testing?

In  Black box testing, the tester checks the expected output based on given inputs. In black-box testing the tester doesn’t have in-depth knowledge about the internal code, data flow and structure of the software. Black box testing is less time consuming, less complex as compared to white box-testing.
Testers who mainly perform non-functional testing such as performance testing, load testing, user acceptance testing etc, come under black-box testing and are called black-box testers.

L. Which testers come under white-box testing?

In white-box testing, testers study and test an internal-structure of software.White-box testing requires in-depth knowledge about coding concepts,application functionality. White box testing is based on transparency i.e  the tester must have the proper knowledge about the internal structure and functionality of the software application. White box testing is time-consuming,complex and expensive

Testers who mainly perform functional testing such as unit testing, loop coverage, path coverage etc come under white-box testing and are called white-box testers.

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