These phases have their own unique functions and goals

1. Waterfall Model

This is the most basic software development life cycle process which is followed broadly in the industry. Here the developers follow a sequence of processes where the processes flow progressively downwards towards the ultimate goal. It is like a waterfall where there are a number of phases.

These phases have their own unique functions and goals. There are, in fact, four phases – requirement gathering and analysis phase, software design, programmed implementation and testing, maintenance. All these four phases come one after another in the given order.

In the first phase all the possible system requirements for developing a particular software are noted and analyzed. This in turn depends on the software requirement specifications which includes detailed information about expectations of the end user. Based on this a Requirement Specification.

Document is created which acts an input to the next phase, i.e. software design phase. What needs to be emphasized here is that once you move into the next phase it won’t be possible to update the requirements. So you must be very thorough and careful about the end-user requirements.

Advantages

Easy to implement and maintain.

The initial phase of rigorous scrutiny of requirements and systems helps in saving time later in the developmental phase

The requirement of resources is minimal and testing is done after completion of each phase.

Disadvantages

It is not possible to alter or update requirements

You cannot make changes once you are into the next phase.

Cannot start the next phase until the previous phase is completed

2. V Model

This model is widely recognized as superior to waterfall model. Here the development and test execution activities are carried on side by side in the downhill and uphill shape. In this model, testing starts at the unit level and spreads towards integration of the entire system.

So, SDLC is divided into five phases – unit testing, integration testing, regression testing, system testing and acceptance testing.

Advantages

Easy to use the model since testing activities like planning and test designing are done before coding

Saves time and enhances chances of success.

Defects are mostly found at an early stage and downward flow of defects is generally avoided

Disadvantages

It is a rigid model

Early prototypes of the product are not available since the software is developed during the implementation phase

If there are changes in the midway, then the test document needs to be updated

3. Agile model

In this SDLC model requirements and solutions evolve through collaboration between various cross functional teams. This is known as an iterative and incremental model.

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Advantages

Ensure customer satisfaction with rapid and continuous development of deliverables.

It is a flexible model as customers, developers and testers continuously interact with each other

Working software can be developed quickly and product can be adapted to changing requirements regularly

Disadvantages

In large and complex software development cases it becomes difficult to assess the effort required at the beginning of the cycle

Due to continuous interaction with the customer, the project can go off track if the customer is not clear about the goals

4. Spiral model

It is more like the Agile model, but with more emphasis on risk analysis. It has four phases – planning, risk analysis, engineering and evaluation. Here gathering of requirements and risk assessment is done at the base level and every upper spiral builds on it.

Advantages

Risk avoidance chance is enhanced due to the importance on risk analysis.

Its a good model for complex and large systems.

Depending on the changed circumstances additional functionalities can be added later on

Software is produced early in the cycle

Disadvantages

Its a costly model and requires highly specialized expertise in risk analysis

It does not work well in simpler projects

5. Rational Unified Process

This model also consists of four phases, each of which is organized into a number of separate iterations. The difference with other models is that each of these iterations must separately satisfy defined criteria before the next phase is undertaken.

Advantages

With an emphasis on accurate documentation this model is able to resolve risks associated with changing requirements of the client

Integration takes less time as the process goes on throughout the SDLC.

Disadvantages

The biggest disadvantage is that the team members need to be experts in their niche.

In big projects such continuous integration, it might give rise to confusions

6. Rapid application development

This is another incremental model like the Agile model. Here the components are developed parallelly to each other. The developments are then assembled into a product.

Advantages

The development time is reduced due to simultaneous development of components and the components can be reused

A lot of integration issues are resolved due to integration from the initial stage

Disadvantages

It requires a strong team of highly capable developers with individual efficacy in identifying business requirements

It is a module-based model, so systems that can be modularized can only be developed in this model

As the cost is high, the model is not suitable for cheaper projects

Conclusion

The above-mentioned software testing models are a part of the SDLC process. With the ever-increasing awareness and need for information technology, has given rise to more than 100+ testing types that are used today in many big companies. These processes keep changing as per the requirements, projects and preferences.