What is Big Bang integration testing?

In Big Bang integration testing all components or modules are integrated simultaneously, after which everything is tested as a whole.

• In this approach individual modules are not integrated until and unless all the modules are ready.
• In Big Bang integration testing all the modules are integrated without performing any integration testing and then it’s executed to know whether all the integrated modules are working fine or not.
• This approach is generally executed by those developers who follows the ‘Run it and see’ approach.
• Because of integrating everything at one time if any failures occurs then it become very difficult for the programmers to know the root cause of that failure.
• In case any bug arises then the developers has to detach the integrated modules in order to find the actual cause of the bug.

Below is the image of the big bang integration testing:

Suppose a system consists of four modules as displayed in the diagram above. In big bang integration all the four modules ‘Module A, Module B, Module C and Module D’ are integrated simultaneously and then the testing is performed. Hence in this approach no individual integration testing is performed because of which the chances of critical failures increases.
Advantage of Big Bang Integration:

• Big Bang testing has the advantage that everything is finished before integration testing starts.

Disadvantages of Big Bang Integration:

• The major disadvantage is that in general it is very time consuming
• It is very difficult to trace the cause of failures because of this late integration.
• The chances of having critical failures are more because of integrating all the components together at same time.
• If any bug is found then it is very difficult to detach all the modules in order to find out the root cause of it.
• There is high probability of occurrence of the critical bugs in the production environment

What is Integration testing?

Integration testing tests integration or interfaces between components, interactions to different parts of the system such as an operating system, file system and hardware or interfaces between systems.

• Also after integrating two different components together we do the integration testing. As displayed in the image below when two different modules ‘Module A’ and ‘Module B’ are integrated then the integration testing is done.
• 

• Integration testing is done by a specific integration tester or test team.
• Integration testing follows two approach known as ‘Top Down’ approach and ‘Bottom Up’ approach as shown in the image below:
  

Below are the integration testing techniques:
1. Big Bang integration testing:
In Big Bang integration testing all components or modules are integrated simultaneously, after which everything is tested as a whole. As per the below image all the modules from ‘Module 1’ to ‘Module 6’ are integrated simultaneously then the testing is carried out.

Advantage: Big Bang testing has the advantage that everything is finished before integration testing starts.
 Disadvantage: The major disadvantage is that in general it is time consuming and difficult to trace the cause of failures because of this late integration.
2. Top-down integration testing: Testing takes place from top to bottom, following the control flow or architectural structure (e.g. starting from the GUI or main menu). Components or systems are substituted by stubs. Below is the diagram of  ‘Top down Approach’:

Advantages of Top-Down approach:

• The tested product is very consistent because the integration testing is basically performed in an environment that almost similar to that of reality
• Stubs can be written with lesser time because when compared to the drivers then Stubs are simpler to author.

Disadvantages of Top-Down approach:

• Basic functionality is tested at the end of cycle

3. Bottom-up integration testing: Testing takes place from the bottom of the control flow upwards. Components or systems are substituted by drivers. Below is the image of ‘Bottom up approach’:

Advantage of Bottom-Up approach:

• In this approach development and testing can be done together so that the product or application will be efficient and as per the customer specifications.

Disadvantages of Bottom-Up approach:

• We can catch the Key interface defects at the end of cycle
• It is required to create the test drivers for modules at all levels except the top control

Incremental testing:

• Another extreme is that all programmers are integrated one by one, and a test is carried out after each step.
• The incremental approach has the advantage that the defects are found early in a smaller assembly when it is relatively easy to detect the cause.
• A disadvantage is that it can be time-consuming since stubs and drivers have to be developed and used in the test.
• Within incremental integration testing  a range of possibilities exist, partly depending on the system architecture.

Functional incremental: Integration and testing takes place on the basis of the functions and functionalities, as documented in the functional specification.

What is Component testing?

What is Component testing?: Component testing is a method where testing of each component in an application is done separately.  Suppose, in an application there are 5 components. Testing of each 5 components separately and efficiently is called as component testing.

• Component testing is also known as module and program testing. It finds the defects in the module and verifies the functioning of software.
• Component testing is done by the tester.
• Component testing may be done in isolation from rest of the system depending on the development life cycle model chosen for that particular application. In such case the missing software is replaced by Stubs and Drivers and simulate the interface between the software components in a simple manner.
• Let’s take an example to understand it in a better way. Suppose there is an application consisting of three modules say, module A, module B and module C. The developer has developed the module B and now wanted to test it. But in order to test the module B completely few of it’s functionalities are dependent on module A and few on module C. But the module A and module C has not been developed yet. In that case to test the module B completely we can replace the module A and module C by stub and drivers as required.
• Stub: A stub is called from the software component to be tested. As shown in the diagram below ‘Stub’ is called by ‘component A’.
• Driver: A driver calls the component to be tested. As shown in the diagram below ‘component B’ is called by the ‘Driver’.

Below is the diagram of the component testing:

As discussed in the previous article of the ‘Unit testing’ it is done by the developers where they do the testing of the individual functionality or procedure. After unit testing is executed, component testing comes into the picture. Component testing is done by the testers.
Component testing plays a very important role in finding the bugs. Before we start with the integration testing it’s always preferable to do the component testing in order to ensure that each component of an application is working effectively.
Integration testing is followed by the component testing.

What is Unit testing?

A unit test is the smallest testable part of an application like functions, classes, procedures, interfaces. Unit testing is a method by which individual units of source code are tested to determine if they are fit for use.

• Unit tests are basically written and executed by software developers to make sure that code meets its design and requirements and behaves as expected.
• The goal of unit testing is to segregate each part of the program and test that the individual parts are working correctly.
• This means that for any function or procedure when a set of inputs are given then it should return the proper values. It should handle the failures gracefully during the course of execution when any invalid input is given.
• A unit test provides a written contract that the piece of code must assure. Hence it has several benefits.
• Unit testing is basically done before integration as shown in the image below.

Method Used for unit testing: White Box Testing method is used for executing the unit test.

When Unit testing should be done?
Unit testing should be done before Integration testing.
By whom unit testing should be done?
Unit testing should be done by the developers.
Advantages of Unit testing:
1. Issues are found at early stage. Since unit testing are carried out by developers where they test their individual code before the integration. Hence the issues can be found very early and can be resolved then and there without impacting the other piece of codes.
2. Unit testing helps in maintaining and changing the code. This is possible by making the codes less interdependent so that unit testing can be executed. Hence chances of impact of changes to any other code gets reduced.
3. Since the bugs are found early in unit testing hence it also helps in reducing the cost of bug fixes. Just imagine the cost of bug found during the later stages of development like during system testing or during acceptance testing.
4. Unit testing helps in simplifying the debugging process. If suppose a test fails then only latest changes made in code needs to be debugged.

What are Software Testing Levels?

Testing levels are basically to identify missing areas and prevent overlap and repetition between the development life cycle phases. In software development life cycle models there are defined phases like requirement gathering and analysis, design, coding or implementation, testing and deployment.  Each phase goes through the testing. Hence there are various levels of testing. The various levels of testing are:

1. Unit testing: It is basically done by the developers to make sure that their code is working fine and meet the user specifications. They test their piece of code which they have written like classes, functions, interfaces and procedures.
2. Component testing: It is also called as module testing. The basic difference between the unit testing and component testing is in unit testing the developers test their piece of code but in component testing the whole component is tested. For example, in a student record application there are two modules one which will save the records of the students and other module is to upload the results of the students. Both the modules are developed separately and when they are tested one by one then we call this as a component or module testing.
3. Integration testing: Integration testing is done when two modules are integrated, in order to test the behavior and functionality of both the modules after integration. Below are few types of integration testing:
   • Big bang integration testing
   • Top down
   • Bottom up
   • Functional incremental
4. Component integration testing: In the example above when both the modules or components are integrated then the testing done is called as Component integration testing. This testing is basically done to ensure that the code should not break after integrating the two modules.
5. System integration testing: System integration testing (SIT) is a testing where testers basically test that in the same environment all the related systems should maintain data integrity and can operate in coordination with other systems.
6. System testing: In system testing the testers basically test the compatibility of the application with the system.
7. Acceptance testing: Acceptance testing are basically done to ensure that the requirements of the specification are met.
8. Alpha testing: Alpha testing is done at the developers site. It is done at the end of the development process
9. Beta testing: Beta testing is done at the customers site. It is done just before the launch of the product.

What is Prototype model- advantages, disadvantages and when to use it?

The basic idea in Prototype model is that instead of freezing the requirements before a design or coding can proceed, a throwaway prototype is built to understand the requirements. This prototype is developed based on the currently known requirements. Prototype model is a software development model. By using this prototype, the client can get an “actual feel” of the system, since the interactions with prototype can enable the client to better understand the requirements of the desired system.  Prototyping is an attractive idea for complicated and large systems for which there is no manual process or existing system to help determining the requirements.

The prototype are usually not complete systems and many of the details are not built in the prototype. The goal is to provide a system with overall functionality.

Diagram of Prototype model:

Advantages of Prototype model:

• Users are actively involved in the development
• Since in this methodology a working model of the system is provided, the users get a better understanding of the system being developed.
• Errors can be detected much earlier.
• Quicker user feedback is available leading to better solutions.
• Missing functionality can be identified easily
• Confusing or difficult functions can be identified
  Requirements validation, Quick implementation of, incomplete, but
  functional, application.

Disadvantages of Prototype model:

• Leads to implementing and then repairing way of building systems.
• Practically, this methodology may increase the complexity of the system as scope of the system may expand beyond original plans.
• Incomplete application may cause application not to be used as the
  full system was designed
  Incomplete or inadequate problem analysis.

When to use Prototype model:  

• Prototype model should be used when the desired system needs to have a lot of interaction with the end users.
• Typically, online systems, web interfaces have a very high amount of interaction with end users, are best suited for Prototype model. It might take a while for a system to be built that allows ease of use and needs minimal training for the end user.
• Prototyping ensures that the end users constantly work with the system and provide a feedback which is incorporated in the prototype to result in a useable system. They are excellent for designing good human computer interface systems.

What is Spiral model- advantages, disadvantages and when to use it?

The spiral model is similar to the incremental model, with more emphasis placed on risk analysis. The spiral model has four phases: Planning, Risk Analysis, Engineering and Evaluation. A software project repeatedly passes through these phases in iterations (called Spirals in this model). The baseline spiral, starting in the planning phase, requirements are gathered and risk is assessed. Each subsequent spirals builds on the baseline spiral. Its one of the software development models like Waterfall, Agile, V-Model.

Planning Phase: Requirements are gathered during the planning phase. Requirements like ‘BRS’ that is ‘Business Requirement Specifications’ and ‘SRS’ that is ‘System Requirement specifications’.

Risk Analysis: In the risk analysis phase, a process is undertaken to identify risk and alternate solutions.  A prototype is produced at the end of the risk analysis phase. If any risk is found during the risk analysis then alternate solutions are suggested and implemented.

Engineering Phase: In this phase software is developed, along with testing at the end of the phase. Hence in this phase the development and testing is done.

Evaluation phase: This phase allows the customer to evaluate the output of the project to date before the project continues to the next spiral.

Diagram of Spiral model:

The spiral model is similar to the incremental model, with more emphasis placed on risk analysis. The spiral model has four phases: Planning, Risk Analysis, Engineering and Evaluation. A software project repeatedly passes through these phases in iterations (called Spirals in this model). The baseline spiral, starting in the planning phase, requirements are gathered and risk is assessed. Each subsequent spirals builds on the baseline spiral. Its one of the software development models like Waterfall, Agile, V-Model.

Planning Phase: Requirements are gathered during the planning phase. Requirements like ‘BRS’ that is ‘Bussiness Requirement Specifications’ and ‘SRS’ that is ‘System Requirement specifications’.

Risk Analysis: In the risk analysis phase, a process is undertaken to identify risk and alternate solutions.  A prototype is produced at the end of the risk analysis phase. If any risk is found during the risk analysis then alternate solutions are suggested and implemented.

Engineering Phase: In this phase software is developed, along with testing at the end of the phase. Hence in this phase the development and testing is done.

Evaluation phase: This phase allows the customer to evaluate the output of the project to date before the project continues to the next spiral.

Diagram of Spiral model:

Advantages of Spiral model:

• High amount of risk analysis hence, avoidance of Risk is enhanced.
• Good for large and mission-critical projects.
• Strong approval and documentation control.
• Additional Functionality can be added at a later date.
• Software is produced early in the software life cycle.

Disadvantages of Spiral model:

• Can be a costly model to use.
• Risk analysis requires highly specific expertise.
• Project’s success is highly dependent on the risk analysis phase.
• Doesn’t work well for smaller projects.

 When to use Spiral model:

• When costs and risk evaluation is important
• For medium to high-risk projects
• Long-term project commitment unwise because of potential changes to economic priorities
• Users are unsure of their needs
• Requirements are complex
• New product line
• Significant changes are expected (research and exploration)

Advantages of Spiral model:

• High amount of risk analysis hence, avoidance of Risk is enhanced.
• Good for large and mission-critical projects.
• Strong approval and documentation control.
• Additional Functionality can be added at a later date.
• Software is produced early in the software life cycle.

Disadvantages of Spiral model:

• Can be a costly model to use.
• Risk analysis requires highly specific expertise.
• Project’s success is highly dependent on the risk analysis phase.
• Doesn’t work well for smaller projects.

 When to use Spiral model:

• When costs and risk evaluation is important
• For medium to high-risk projects
• Long-term project commitment unwise because of potential changes to economic priorities
• Users are unsure of their needs
• Requirements are complex
• New product line
• Significant changes are expected (research and exploration)