What are different boundary related defects?

Like there is a separate testing methodology for each aspect of a software system, there is a testing technique called “boundary value analysis” for testing the boundary values of a software system or application.

WHAT IS BOUNDARY VALUE ANALYSIS?
- Boundary value analysis consists of test cases which include the boundary value representatives of the software program.
- Boundary values are the values which lie on the maximum and minimum edges of an equivalence partition.
- These maximum and minimum values can be either input values or output values of the software program.
- These boundary values of the software are the main seat for the defects or errors that are responsible for the faults in the software.
- This property of the boundary values finds them useful in the test cases.
- These input and output values are taken from the specifications of the component.
- The values contained in each of the sets are processed by the software system or application exactly in the same way.
- While creating the test cases for the boundary value analysis it is very important to keep in mind both the invalid and valid partitions even though there is no need for invalid partitions.
- Whenever an invalid partition is encountered by the application, the test case is designed as such that it helps the application control the partition in a proper way instead of faltering.
- The boundary is located exactly between any two set partitions and the behavior of the software system or application.
- The value at a boundary can either be maximum or minimum.
- The values at the boundaries are absolute and cannot be exceeded.
- In order to make correct assumptions about the software system or application you need to understand the boundary limits correctly.
- Apart from boundaries there are threshold values and these values cannot be exceeded unless modified.
- The threshold values can be modified to suit your needs.
- But you should keep in mind that hanging the threshold values can affect the performance of your input data.
- The boundary values are generated and verified through observation and testing. - While testing the workload is increased till the software system starts giving its maximum efficient performance.
- Some of the components of a system have capability to handle more loads than the other components.
- In such a case the average value of the load should be calculated and assigned to the software system or application.
- High latency is showed by some of the features and functionalities as compared to the others which operate under acceptable values.
- In such a case the maximum value is calculated on the basis of the usage of the features and functionality such that the overall performance of the software system or application remains unaffected and acceptable.
- If some of the components are operating on the limits exceeding those limits that were used during the testing, the acceptable limits of the other components will be affected.

Therefore, it is important to implement a good capacity management so that effective limits are established. We are now clearly stating some boundary related defects:


1. Numeric boundaries
2. Boundary on numerosity
3. Boundary within the data structures
4. Equality as a boundary
5. Boundary on space
6. Boundary in loops
7. Boundary in time
8. Errors in calculations
9. Out- dated constants
10.Invisible boundaries
11.Hardware related boundaries

What are different startegies for black box testing?

Writing and executing test cases is an expensive task. Whatever test case is written, it should hint towards a different mode of failure. Testing strategies for black box testing are:
- Customer Requirements tests
Requirements are very important for black box testing. Each and every customer requirement should be tested. To do this, every requirement is traced to its test case and every test case to its customer requirement. The first test case is to write a most used success path ( a path that is error condition free) and proceed by planning more success paths. Some failure paths (a path that has errors in it) are also planned. Execution of tests is done so that risky requirements are tested first. It would give more time to fix the errors before the product delivery.

- Equivalence Partitioning
It is a strategy that reduces the number of test cases that are needed to be developed. The input domain is divided into classes. Test cases should be designed so that the inputs lie within these equivalence classes. For each equivalence class, set of data should be treated same by the module under test and should produce same result.

- Boundary Value Analysis
Mistakes generally occur at boundaries of the equivalence classes. Boundary value analysis guides you to create test cases at the boundaries of equivalence classes. Boundary value is defined as a value that relates to a minimum or maximum input.

- Decision Table Testing
To record business rules, decision tables are used. In decision tables, conditions represents input conditions, actions represent events that should trigger. Each column in table is a unique combination of input condition resulting in initiating an action associated with rule. Each rule or column becomes a test case.

- Failure Test Cases
The program or the application should be robust which means that it should respond properly in case or erroneous user input.

Some Black box testing techniques...Graph based testing methods, Error guessing and Boundary Value Analysis.

Graph Based Testing Methods
Software testing begins by creating a graph of important objects and their relationships and then devising a series of tests that will cover the graph so that each objects and their relationship is exercised and errors are uncovered.Graph based testing begins with the definition of all nodes and node weights i.e. objects and attributes are identified.

Error Guessing
The purpose of error guessing is to focus the testing activity on areas that have not been handled by the other more formal techniques, such as equivalence partitioning and boundary value analysis. It comes with an experience of technology and the project. There are no specific tools and techniques for error guessing but you can write test cases depending on the situation. Error guessing will require tester to think out of the box and would involve intuition and experience of the tester.

Boundary Value Analysis (BVA)
It is a test data selection technique where the extreme values are chosen. It makes use of the fact that the inputs and outputs of the component under test can be partitioned into ordered sets with identifiable boundaries. A test engineer chooses values that lie along data extremes. It is expected that if the system works correctly for these special values, then it will work correctly for all values in between. The boundary value analysis test cases are obtained by holding the values of all but one obtained by holding the values of all but one variable at their nominal values, and letting that variable at their nominal values, and letting that variable assume its extreme values variable assume its extreme value.
There are two ways to generalize BVA technique :
- By the number of variables: for n variables, BVA yields 4n+1 test cases.
- By the kinds of ranges.

Advantages of Boundary Value Analysis
- Robustness Testing
- It checks values for min-1, min, nom, max-1, max, max+1
- It forces attention to exception handling.

Limitations of Boundary Value Analysis
BVA works best when the program is a function of several independent variables that represent bounded physical quantities.
Boundary value analysis works well when the program to be tested is a function of the program to be tested is a function of several severalindependent independent variables that variables that represent bounded represent bounded physical physicalquantities quantities.

Methods of black box testing - Boundary Value Analysis

Black Box Testing is testing without knowledge of the internal workings of the item being tested. There are four black box testing methods. Graph based testing method and Equivalence Partitioning have already been discussed.

Boundary Value Analysis
Boundary Value Analysis determines the effectiveness of test cases for a given scenario. Boundary Value Analysis (BVA) is a test Functional Testing technique where the extreme boundary values are chosen. Boundary values include maximum, minimum, just inside/outside boundaries, typical values, and error values. Boundary value analysis complements and can be used in conjunction with equivalence partitioning.
For boundary value analysis, the following guidelines should be used:
- For input ranges bounded by a and b, test cases should include values a and b and just above and just below a and b respectively.
- If an input condition specifies a number of values, test cases should be developed to exercise the minimum and maximum numbers and values just above and below these limits.

Advantages of Boundary Value Analysis
- Robustness Testing – Boundary Value Analysis plus values that go beyond the limits.
- Min – 1, Min, Min +1, Nom, Max -1, Max, Max +1.
- Forces attention to exception handling.

Limitations of Boundary Value Analysis
Boundary value testing is efficient only for variables of fixed values i.e boundary.