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Software Development Life Cycle VS Software Testing Life Cycle (SDLC and STLC)


Interest is the factor that drives resources, clients, CEO, managers, stakeholders, and the development team to complete a project successfully. Along with money, time and brand value too influence people’s behavior. This is the reason why the comparison of SDLC vs STLC came into the role. Both these are connected to some extent and we can say one is the predecessor of the other. It is clear that if an application is developed to serve an objective then it should be tested thoroughly before it is deployed to the market. You must be wondering knowing that clients are investing huge amount of money after development and testing for a successful deployment.

This was the story behind the existence of SDLC and STLC. Now you should learn the difference between sdlc and stlc. Before we actually discuss the comparison, let us first understand what is the sdlc and stlc life cycle in software. Once you will understand both of these concepts in depth then we will discuss sdlc vs stlc in software testing and how are they different and what are the activities needed for a successful ending?

What is SDLC? Software Development Life Cycle Explained

The life cycle is generally defined as a series of changes in one’s life. Either it is living or nonliving, anything that has a complete series of steps is taken as the life cycle. These sequences have a starting and end point too. On a contrary note, we can say that every process has a set of sub-processes within it. Let us take this discussion ahead towards software development. So, SDLC in software testing means the life cycle of a software development process.

There are no predefined rules because a series of steps that are working well for one model may behave badly in another model. Let us see a few examples of SDLC models ahead.

SDLC and STLC life cycle - SDLC Models

  • Waterfall Model – This is the most classic model.
  • V-Model – This is the most popular model.
  • Spiral Model
  • Iterative Model
  • Agile Model – This is the latest and most suitable SDLC model available so far.

It would not be wrong if we say that agile scrum model practices are just wonderful and working the best for the IT industry but you are always free to choose any of these models. If requirements are clear and not expected to change in the future then developers will prefer the waterfall model in that case, not the Agile ones.

Now, let’s move on to discuss in detail the sdlc and stlc life cycle.

Software Development Life Cycle Phases

There are Six Software development life cycle phases. Let us discuss each of the phases in detail one by one.

Software Development Life Cycle Phases

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1). Planning Phase of SDLC

Every time you start a project, there should be certain planning behind it. Obviously, planning is the first phase that comes even before the paperwork. In this phase, high-level details are considered from the project point of view. There is a need for dedicated resources behind this phase. Here, all possible cons and pros will be discussed and how to maximize the ROI is also discussed within the planning phase.

This phase involves plenty of rework to overcome any hindrance behind the project success. The basic idea behind the planning phase is that to convert a thought or idea into reality it should be followed by a sequence of steps to achieve success. Planning again is based on a particular set of outcomes. When building new software, this is crucial to study the project feasibility and even if it will be updated after a few years or not.

2). Analysis Phase of SDLC

Once the planning phase is completed, then it comes to the analysis where the team is performing several tasks before attaining any particular solution. Here, first, you will perform the project feasibility study, estimate the workloads, project costs, requirement gathering, analysis, and scheduling.

The intention of this phase is clear to make a final check before actually starting the work. If there are any shortcomings then it can be removed by communicating with stakeholders or the development team. Don’t forget to focus on the pros and cons here.

3). Design Phase of SDLC

Now planning is done and requirements are also clear. Here, the team needs some references before they actually start the work. Designers also have a crucial role here. Also, you need to define the project functionalities and check how many screens should be there for each section. In brief, every bit of detail will be designed minutely in this phase.

For example, if a customer wants to book the flight then requirements are clear and the designer will design screens to cover the functionalities that will be performed by a particular software program. The designer will also give an idea of layouts, working plans, process diagrams, and several other types of documentation too. The concerned person will choose the best path to go ahead.

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4). Coding Phase of SDLC

Till this stage, all major decisions are already taken. The intention of the coding phase is to replicate the design works into a piece of the software program. Developers play an important role here and are responsible for designing reusable codes. In this phase, lots of discussions are made related to the framework and finally, the best one is selected based on the requirements.

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There are plenty of programming tools that can be used side by side to make the development work easier and faster. Keep in mind that this is the most difficult phase and the development of a complete software program is neither easy nor small. There is a big chunk of work and it needs to be divided into small chunks further. Set the priority for each of the modules and complete them one by one as per the urgency. Rate then based on their functionalities. This is the biggest phase of development where you need to put maximum effort to complete a particular task.

5). Testing Phase of SDLC

As the name suggests, this phase is all about testing and developing a piece of the software program before it is given to clients or end users. There are plenty of test methodologies that are performed by testers to find any defects in the software.

6). Maintenance Phase of SDLC

This is an after-sales service that is signed to maintain a product for a longer time period. If there are any issues in the software program then it is addressed by the development team immediately and all possible bugs are resolved on time. It is related to future enhancements too if needed.

What is STLC? Software Testing Life Cycle

STLC is defined as the sequence of activities conducted to perform software testing. These activities are performed methodologically to certify a software product. There are different phases in STLC and each of them has a definite Entry and Exit criteria, activities, and deliverables associated with it. In the ideal world, you will never switch to the next stage until the exit criteria of the previous stage are met.

Software Testing Life Cycle

Now let’s discuss each of the phases in detail below.

  • Requirement Analysis

This is the first phase in STLC where the QA team will check the testing requirements for the whole project. For a depth understanding, the QA team is generally following clients. It will be opted when only testing is needed, not the development. The basic categories under this phase include – Entry criteria, activities performed, and deliverables too.

  • Test Planning

This is another crucial phase in the STLC. Here, time estimates are calculated before testing is actually started. The outcome of this phase is test plans or documentation. Once you have completed this phase successfully, the QA team can start with development activities.

  • Test Development

Here, the actual development of test cases will take place once the test planning is completed. Here, not only the test cases but a complete report that contains test data is documented. Once it is done, the report will be cross verified by QA leads. In this phase, RTM is also prepared. Documents are generally tracked in both ways either forward or backward.

  • Environment Setup

This is not practiced because the environment is generally decided in advance in the SDLC phase only. The QA team will not make any changes to the environment.

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  • Test Execution

Here, tests are executed based on test plans prepared earlier. If they are alright then marked as Pass otherwise Fail. The QA team will also prepare a complete list of bugs in this phase that are further forwarded to the development team to fix issues.

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  • Closure

In this phase, a decision will be made where the team will decide what went right and what was wrong from test perspectives. If you are sure what to improve for the future then it will save time and money both. 

Now that we have covered sdlc and stlc life cycle completely, let’s talk about the difference between sdlc and stlc:

Difference between SDLC and STLC

Features SDLC STLC
Origin Development Life Cycle Testing Life Cycle
Relationship It is taken as the predecessor It is defined as the successor
Definition It includes the development of software including testing and other phases. It is related to the testing of a software project.
Requirement Gathering BA will gather requirements and developer will perform the development. Here, the testing team will check the software from the functional or non-functional point of view.
Intention/Objective SDLC is intended for the journey of successful software development. STLC is needed to find any pitfalls or shortcomings in the testing phase.
Design In SDLC, there is one technical architect who is responsible for adding extra quality to the software. In SDLC, the technical architect does test planning and he will also identify high-level testing points too.
Coding Here, the actual code is developed as per the design structure emphasized. In STLC, the behavior of developed modules will be tested and verified.
Testing Here, the code is tested by peer developers. Here, unit testing, integration testing, and system testing are performed together. Here, testing and reporting work is done together. Keep in mind unlike code testing, here functional or non-functional behavior is tested.
Phases Planning, Analysis, Design, Development, Testing, Maintenance Requirement Analysis, Test Planning, Test Development, Environment Setup, Test Execution, Test Closure

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The discussion is pretty clear. We hope that you could completely understand the sdlc and stlc life cycle, sdlc vs stlc in software testing, and the difference between sdlc and stlc; where one is a development approach and the other is the testing approach as a whole. Although testing comes under SDLC phases too, here testing is performed in a much different way when compared to the STLC. Keep in mind that STLC is always defined under the SDLC. The concerned activities for each section are generally different.

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