Explain Black box and White box testing? What are their advantages and disadvantages?

For complete testing of a software product both black and white box testing are necessary.

Black-box testing
This testing looks at the available inputs for an application and the expected outputs that should result from each input. It does not have any relation with the inner workings of the application, the process undertaken or any other internal aspect of the application. Search engine is a very good example of a black box system. We enter the text that we want to search, by pressing “search” we get the results. Here we are not aware of the actual process that has been implemented to get the results. We simply provide the input and get the results.

White-box testing
This testing looks into the complex inner working of the application; it tests the processes undertaken and other internal aspects of the application. While black box testing is mainly concerned with the inputs and outputs of the application, white box testing help us to see beyond i.e. inside the application. White-box testing requires a degree of sophistication which is not the case with the black-box testing, as the tester is required to interact with the objects that are used to develop an application rather than having easy access to the user interface. In-circuit testing is a good example of a white-box system testing where the tester is looking at the interconnections between different components of the application and verifying the proper functioning of each internal connection. We can also consider the example of an auto-mechanic who takes care of the inner workings of a vehicle to ensure that all the components are working correctly to ensure the proper functioning of the vehicle.

The basic difference between black-box and white-box testing is the areas of focus which they choose. We can simply say that black-box testing is focused on results. Where if an action is performed and the desired result is obtained then the process that has actually been used is irrelevant. White-box testing, on the other hand focuses on the internal working of an application and it is considered to be complete only when all the components are tested for proper functioning.

Advantages of Black-box testing
- Since tester does not have to focus on the inner working of an application, creating test cases is easier.
- Test case development is faster as tester need not to spend time on identifying the inner processes; his only focus is on the various paths that a user may take through GUI.
- It is simple to use as it focuses only on valid and invalid inputs and ensures that correct outputs are obtained.

Drawbacks of Black-box testing
Constantly changing GUI makes script maintenance difficult as the input may also be changing. Interacting with GUI may result in making the test script fragile and it may not properly execute consistently.

Advantages of White-box testing
- Since the focus is on the inner working the tester can identify objects pro grammatically. This can be useful when the GUI is frequently changing.
- It can improve stability and re usability of test cases provided the object of an application remains the same.
- By testing each path completely it is possible for a tester to achieve thoroughness.

Drawbacks of White-box testing
Developing test cases for white-box testing involves high degree of complexity therefore it requires highly skilled people to develop the test cases. Although to a great extent fragility is overcome in white-box testing BUT change in the objects name may lead to breaking of the test script.

What is Software Process? What do you mean by software quality factors? What are different process models?

The factors that affect the quality of the software are called quality factors. The software product quality has three dimensions and each of the dimension deals with a set of quality factors.

PRODUCT OPERATION
- Correctness
- Reliability
- Efficiency
- Integrity
- Usability
PRODUCT TRANSITION
- Portability
- Re usability
- Interoperability
PRODUCT REVISION
- Maintainability
- Flexibility
- Testability

Software process is a set of activities, together with ordering constraints among them, such that if the activities are performed properly and in accordance with the ordering constraints, the desired result is produced.
Software process deals with the technical and management issues of software development.
The different process models are:
- Waterfall Model
The phases of the model are organized in a linear order.
- Prototyping
A throw away prototype is built instead of freezing the requirements before design or coding to help understand the requirements.
- Iterative
The software should be developed in increments with each functionality added to each increment.
- Spiral
Software development activities are organized like a spiral that has many cycles. The radial dimension represents the cumulative cost and the angular dimension represents the progress.

What is Software Project Management? List the number of tasks it consists.

In Software Project Management, the end users and developers need to know the length, duration and cost of the project. It is a process of managing, allocating and timing resources to develop computer software that meets requirements. It consists of eight tasks:
- Problem Identification
- Problem Definition
- Project Planning
- Project Organization
- Resource Allocation
- Project Scheduling
- Tracking, Reporting and Controlling
- Project Termination

In problem identification and definition, the decisions are made while approving, declining or prioritizing projects. In problem identification, project is identified, defined and justified. In problem definition, the purpose of the project is clarified. The main product is project proposal.

In project planning, it describes a series of actions or steps that are needed to for the development of work product. In project organization, the functions of the personnel are integrated. It is done in parallel with project planning.

In resource allocation, the resources are allocated to a project so that the goals and objectives are achieved. In project scheduling, resources are allocated so that project objectives are achieved within a reasonable time span.

In tracking, reporting and controlling, the process involves whether the project results are in accordance with project plans and performance specification. In controlling, proper action is taken to correct unacceptable deviations.

In project termination, the final report is submitted or a release order is signed.

What are steps involved in deriving test cases? What are Validation, Alpha, Beta testing? What are test metrics?

The steps in deriving the test cases using use cases are:
- Using the RTM, the use cases are prioritized. Importance is gauged based on the frequency with which each function of the system is used.
- Use case scenarios are developed for each use case. The detailed description for each use case scenario can be very helpful in later stage.
- For each scenario, take at least one test case and identify the conditions that
will make it execute.
- Data values are determined for each test case.

After system testing is culminated, validation testing is performed which consists of a series of black box tests. It focuses on user-visible actions and user-recognizable output.
Alpha and Beta Testing are a series of acceptance tests. Alpha testing is performed in a controlled environment normally at developer's site. In alpha testing, developers record all errors and usage problems while end users use the system. Beta testing is done at customer's site and developers are not present. In beta testing, end-users records all errors and usage problems.

The amount of testing effort needed to test object oriented software can be indicated by the metrics used for object-oriented design quality. These metrics are:
- Lack of Cohesion in Methods (LCOM)
- Percent Public and Protected (PAP)
- Public Access To Data Members (PAD)
- Number of Root Classes (NOR)
- Number of Children (NOC) and Depth of the Inheritance Tree (DIT)

What is Test Driven Development Methodology and its benefits?

Test-driven Development(TDD)is a method of developing software that adopts a test
first approach plus refactoring. The test-first approach is a programming technique, involving analysis, design, coding and testing all together. Refactoring is used to improve the design of the code without changing the observable behavior of the software, it changes the internal structure. It is cleaning up the bad code. In test-driven development, each new test provides feedback into the design process which helps in driving design decisions.

WHAT ARE DIFFERENT BENEFITS OF TEST DRIVEN DEVELOPMENT

- It allows simple incremental development.
- It involves a simpler development process.
- It provides constant regression testing.
- It improves communication.
- It improves understanding of required software behavior.
- It centralizes knowledge.
- It improves software design.

WHAT ARE DIFFERENT STEPS IN TEST DRIVEN DEVELOPMENT

- Write a test that defines how the software should behave.
- Make the test run as easily and quickly as possible.
- Clean up the code.

After integration testing, the system is tested as a whole for functionality and fitness of use. It includes performance testing, stress testing, security testing, recovery testing.
In object oriented, test requirements are derived from analysis artifacts or work products that use UML such as the class diagrams,sequence diagrams and collaboration diagrams. Use case diagram is a good source to derive test cases. They represent high functionality. Use cases are not independent. They have sequential dependencies. A scenario is an instance of a use case, or a complete path through the use case.

How are programs tested? Explaining Unit Testing and Integration Testing

In testing programs, individual units are tested and this comes under unit testing. Then, their relationship with one another is tested which comes under integration testing.

UNIT TESTING

- It tests the smaller building blocks of a program.
- It confirms that each module performs its assigned task.
- It involves testing the interface, local data structures, boundary conditions, independent paths and error handling paths.
- Two things are used for unit testing : Driver and Stub.
- Driver is a program that accepts test case data, passes data to the component to be tested, and prints relevant results.
- Stub is program that performs support activities such as data manipulation, queries of states of the component being tested and prints verification of entry.

INTEGRATION TESTING

- Integration testing is followed after unit testing.
- All classes are tested for integration.
- Each component performs correctly within collaboration and that each interface is correct.
- Integration testing can be done by thread based testing approach. A thread is a path of communication among classes that needs to process a single input or respond to an event.
- Regression testing is re-execution of some subset of tests to ensure that changes have not produced unintended side effects.

Software Test Case Design Methods - Black Box Testing Methods

Black box testing focuses on:
- testing thefunctional aspect of the software.
- input conditions are derived that will test all functional requirements.
- set of test cases that finds incorrect or missing functions.
- interface errors.
- data structure errors.
- external database excess errors.
- performance errors.
- initialization and termination errors.

Black box techniques include:

- Graph based testing is a black-box testing technique that uses objects that are modeled in software and the relationships among these objects. Steps involved in designing test cases using graph based testing are:

STEP 1: Create a graph of software objects and identify the relationship of these objects.
STEP 2: Traverse the graph to define test cases.

- Equivalence Testing
A black box testing technique which divides the input domain into partitions or into sets of data from which test cases can be derived. These test cases are used to uncover errors. It makes use of equivalence classes which are sets of valid and invalid states that an input may be in.

- Boundary Value Testing
It is a black box testing method that uses the boundaries of the input domain to derive test cases. If input condition specifies range bounded by n and m, the test cases that can be derived use values n and m, just above n and m, just below n and m.

If input condition specifies number of values, the test cases that can be derived are use the minimum, use the maximum, just above and below minimum, just above and below maximum.