Agile vs. Waterfall: Which is the Best Methodology for Your Project?

All You Need to Know About Agile Vs Waterfall Methodologies: Know what is the exact difference between Agile and Waterfall methodology of Software Development and which is the best suitable model for your project with pros and cons of each.

Initially, it is very important for us to know the basic meaning of the terms Agile and Waterfall, before exploring the differences between them.

In simple English, Agile means ‘able to move quickly and easily’ and hence that is what it means when it comes to the Agile development methodology

Agile vs Waterfall

Introduction

Agile is a method of the project management that is represented by splitting of tasks into shorter segments of work with frequent reviews and adaptation of plans.

Similarly, the word waterfall denotes a vertical flow of water or the flow of water through a series of steep drops.

This same illustration applies to the concept of project management when it comes to the waterfall model. It is a method of project management that is represented by serial stages and a fixed plan of work.

development-methods

[image source]

The waterfall model is a linear sequential model in which the progress flows majorly in one direction downwards through the phases of requirement gathering, analysis, design, development, testing, deployment, and maintenance.

The whole finished product is delivered once to the customer at the end of the deployment phase. This is the oldest model for software development.

In the Agile approach for software development, the whole project is broken down into small manageable units. Agile is based on iterative development model where the requirements and solutions grow through a collective effort of self-disciplined & cross-functional teams and their customers/stakeholders.

There are multiple iterations (often called as Sprints) of adaptive planning, design, development, testing (these phases also overlap with each other in the sprint) and delivery. At the end of each sprint, a MVP is delivered. MVP is agreed to a subset of the product features.

Agile persuades quick and flexible response to change. There is a broad range of software development frameworks under Agile. Some of the familiar frameworks include Scrum and Kanban.

With this basic understanding, let us start with a comparison table between agile and waterfall. This table will give you further insight between these two methodologies and the differences between them.

Agile Vs Waterfall Comparison Table

WaterfallAgile
Waterfall methodology is a model in which each stage of the product’s lifecycle occurs in a sequence.

The progress of the project flows gradually downwards through these phases resembling a waterfall.
Agile methodology is a model that follows a sequential, linear and iterative approach.
This model believes in one-time massive whole delivery.

The product is delivered at the end of the SDLC.
This model believes in multiple small chunks of delivery at defined time intervals.

A MVP (Minimum Viable Product) is delivered at the end of each sprint.
Its a traditional and old-fashioned approach.Its a new and modern approach.
One single cycle and single release.Repetitive number of iterations and multiple releases.
It divides the software development lifecycle into different phases.It divides the software development lifecycle into sprints.
Waterfall processAgile process
The process is treated as one single project which is further divided into different phases.The process is divided into multiple projects and each project has an iteration of different stages.
Structured and rigid model.This model is known for its flexibility.
Long-term planning scale.Short term planning scale.
A long distance exists between the customer and the developer.A short distance exists between the customer and the developer.
Long time between specification and implementation.Short time between specification and implementation.
Takes a long time to discover problems.Problems are discovered quickly.
High project schedule risk.Low project schedule risk.
Less ability to respond quickly to changes.High ability to respond quickly to changes.
Testing phase occurs only after the completion of the development phase.Testing is generally performed in parallel with the development to ensure quality continuously.
The customer is involved only at the requirement gathering phase and after that there is no involvement of the customer.

He comes into the picture only at the time of delivery of the product.
The customer is involved throughout the project and feed back is taken from the customer from time to time to ensure customer satisfaction.
Suitable for projects which have clearly defined requirements and those which are not expecting changes.Suitable for projects which have to evolve and those which involve changing requirements.
Stringently sequential process.Highly collaborative software development process leads to better team efforts and quick problem-solving.
Exhibits a project mindset.Introduces a product mindset and thus it is more customer focused.
Formal and hierarchical. The project manager is the decision maker.It is Informal. The entire team is responsible for decision making.
This model anticipates that there will be no changes throughout the project.This model is based on adaptation and it embraces changes.

What's the Difference Between Agile and Waterfall Methodology

Let's explore the pros and cons of agile and waterfall models in detail.

Waterfall Model

Given below are the various Pros and Cons of the Waterfall Model

Waterfall Pros:

  • Forward & backward planning and implementation is easy.
  • The waterfall model is simple to use and easy to understand. Does not require any special training for project managers or employees. It has an easy learning curve.
  • Being rigid in nature, it is easy to manage the waterfall cycle. Each phase has fixed deliverables and a review process.
  • Less complexity as the phases does not overlap. Phases are followed one after the another. It uses a clear structure when compared to the other software development methodologies. The project goes through fixed sequential steps starting from the requirement gathering and finally lands up at maintenance.
  • Due to phased development, discipline is enforced, and timescales can be kept easily.
  • Works good for small projects where we have fixed and crystal-clear requirements.
  • Processes and results are well-documented.
  • Arranging tasks is easy.
  • It is easy to measure the progress as the start and end points of each phase is predetermined.
  • There is almost no change in the requirements throughout the project, hence the tasks remain stable for the developers. Also, it is easy for any new developer to quickly learn and start the work.
  • There are no financial surprises. Once the requirements are fixed, the final cost can be calculated before starting the development.
  • Caters for a sequential funding model.
  • Its detailed design makes the final expected outcome very clear to everyone.
  • The functional requirement specification documented in the requirement gathering phase gives enough details to the testers to design test scenarios and test cases. Hence, the testing process becomes easy in the waterfall model.

Waterfall Cons:

  • As all the requirements must be clearly known before starting the development, it delays the project.
  • Requires extensive research into the user needs.
  • At the initial phase of the project, it is challenging for a customer to clearly define and conceptualize their requirements in the form of functional specifications. Hence, there is a high possibility for them to change their minds after seeing the end product. This change can also occur due to a business plan or market influence. Low flexibility in this model makes it difficult to accommodate any such changes, especially when the product needs to be re-engineered to a large extent.
  • No working model is produced until the later stage during the waterfall lifecycle.
  • Slow delivery times. The customer is not able to see the product until it is fully completed.
  • The customer has no opportunity to get familiar with the system in advance. Waterfall model is more of an internal process and keeps the end user excluded.
  • The client is not informed well about the health of the project.
  • Deadlines can be missed if strict management and regular monitoring are not kept.
  • There is no room for changes even if it is visible during the development as the product is not going to cater to the market requirement.
  • Delays testing until after completion. Also, large revisions are very costly at this point.
  • High risk and uncertainty are involved in the waterfall model as there is too much room for issues to remain unnoticed until the project comes near to completion.
  • Not a suitable model for long, complex and ongoing projects.
  • It is difficult to measure the progress within each phase.

Agile Model

Enlisted below is the list of both Pros and Cons of the Agile Model.

Agile Pros:

  • One of the biggest advantages of the agile model is its great adaptability. Adaptability means ‘responding to change’. Agile is very flexible in dealing with the changes in customer needs and priorities.
  • Allows to constantly refine and re-prioritize the overall product backlog without affecting the current iteration in which the team is focused on delivering the MVP. The changes can be planned for the next iteration, thereby offering an opportunity to bring in the changes within a few weeks only.
  • Agile methodology offers a great degree of stakeholder engagement. The client and the project team meet before, during and after each sprint. As the customer is constantly involved throughout the project, there are more opportunities for the team to clearly understand the customer’s vision.
  • The working software is delivered early and frequently. This increases the stakeholder’s trust in the team and encourages the team to stay highly committed to the project.
  • This model gives transparency. Both the stakeholders and the team know well about what is happening. The client can see the work in progress.
  • Fixed schedule sprints of one to four weeks allow for early and predictable delivery. New features are released quickly and frequently in a time-boxed manner.
  • Agile is customer-centric. It does not just deliver the functionality but also focuses on delivering the feature that is of some value to the user. Each user story has a business focused acceptance criteria.
  • Valuable customer feedback is gained early in the project and changes to the product can be made as required.
  • The focus is on business value. It first delivers what is most important to the client.
  • Improves the quality of deliverables. Unlike waterfall, testing is continuously and frequently done in an Agile project and that, in turn, helps in detecting and fixing the issues early.
  • Agile supports TDD (Test Driven Development) approach which provides enough time to create unit tests for the features that are going to be released through MVP.
  • Also, by producing frequent builds, any misalignment with the customer requirements can also be detected and fixed early.
  • As we get immediate user feedback after each MVP release, the risk of project failure is low, when you are working in an Agile way.
  • Agile promotes teamwork. There is a great collaboration, interaction, harmony and enthusiasm among the Agile team members.
  • The cost and schedule estimates of each sprint are communicated to the client prior to the start of the sprint. This improves decision making as the user can understand the cost of each feature and prioritize accordingly.
  • In an agile project, there is a room for continuous improvement. Lessons learned from the past sprints can be applied in the upcoming sprints.

Agile Cons:

  • It is often seen that Agile teams have a tendency to neglect documentation. This is because the Agile manifesto focuses more on working software than the comprehensive documentation. However, the teams should maintain the right balance between the code and documentation.
  • As it requires a high degree of customer involvement, it can sometimes be problematic for customers who do not have much time and interest to participate in the project.
  • Does not works well if the team is lacking commitment and dedication. Waterfall requires involvement, however, Agile requires commitment.
  • If the initial architecture and design are weak, then frequent refactoring is required.
  • When compared to the waterfall, Agile is difficult to practice. The team members must be well versed with Agile concepts. It requires a lot of discipline and commitment to practice Agile.
  • Due to re-prioritization, it is less predictable than what will be delivered at the end of the sprint.
  • Due to time-boxed delivery and frequent re-prioritization, there are chances for a few features to not get delivered in the allocated timeline. This can lead to additional sprints and additional costs. This can also lead to the problem of nebulous timelines.
  • Lack of structure when compared to the waterfall, it demands self-disciplined, highly proficient and cross-skilled teams. Without this, the project can really be a challenging one.
  • Availability is less of a blueprint of the final deliverable.
  • Sometimes the external stakeholder can't resist following the Agile approach. In such cases, training and education about Agile are required to a wide audience.

We had enough discussion about the differences between Agile & waterfall methodologies and the benefits & challenges of each. Let us now explore the differences between agile and waterfall testing.

From the perspective of software testing, it is important for us to have a fair idea about how Agile testing is different from Waterfall testing.

Differences Between Agile and Waterfall Testing Methodology

Waterfall TestingAgile Testing
Testing begins after the completion of the development and builds phases.Testing starts concurrently with the development phase.
Planning is done just once before the testing phase.Planning is done before the project starts and is often done during the project.
The test plan is rarely reviewed during the project.The test plan is reviewed after every sprint.
It is quiet challenging for the testing team to propose any changes in the requirements.The test team actively participates in the requirement gathering and change process.
Test cases are created once for all the functionalities.Test cases are created sprint by sprint for the functionalities that need to be released in each sprint.
Acceptance testing is performed once by the client after the release.Acceptance testing can be done after each iteration and before the delivery by a business analyst or the test team.

Later, it is done by the customer after every release.
Test teams and the development teams are separated by a clear boundary and there is a strict and formal communication between them.Test team and the development teams are integrated as one team and there is a free flow of communication between them.
Verbose and extensive test documentation.Test documentation is done only as much as necessary.
Test estimates and assignments are often the responsibility of the test manager.Test estimates and assignments are the shared responsibility of the team and the test engineers who are involved in providing the estimates and choosing their tasks.
Regression testing is rarely done, and it involves execution of all the test cases.Regression testing is done after each iteration and it involves only those test cases that are required.

Conclusion

In this article, we learned the exact differences between the modern Agile approach and the traditional waterfall method of software development and testing with a comparison table covering the pros and cons of each model.

Hope this information will be helpful for you to decide which is the best model for your project. You may also go for the hybrid model removing all cons of each method – discussed here.