SDLC vs STLC – What’s the Difference?

The Software Development Life Cycle (SDLC) and the Software Testing Life Cycle (STLC), despite their similar names, are two different and distinct methods for guaranteeing project success in software development. Let's look at how you may get the most of both of them for your software development project −

What is Software Development Life Cycle?

The Software Development Life Cycle (SDLC) is a term that refers to the process of creating software.

Based on a research paper by Dr. Winston Royce released in 1970, the Software Development Life Cycle (SDLC) is a linear sequence of processes for delivering software. The procedure is as follows −

Gathering Requirements

Once a gap or opportunity in the organization's application landscape has been found, it is necessary to fully comprehend and record the business requirement in order to choose the best solution. During this phase, it's critical to avoid the temptation to leap to a solution right away, and stakeholders may want coaching and assistance to keep an open mind regarding any solution preferences they may already have.

At this point, it's critical to make sure that current apps don't meet, or can't meet, the criteria. By gathering requirements and reviewing the current application portfolio, solution architects, business analysts, and others with comparable skill sets can assist in this step.

It's always a good idea at this point to reach out to other people across the organization to see whether the identified or comparable needs are also needed in other areas, in order to avoid building or procuring duplicate systems and allowing the system to be reused.

This phase's main result will be a business requirements document (BRD), which will include a list of all necessary functionality, maybe prioritized using an approach like MoSCoW (Must have/Should have/Could have/Won't have now), and with proper traceability by business area.


The design work may begin after the requirements for the new program have been suitably documented and approved off. At this stage, businesses should consider if their resources would be better spent constructing a custom system or buying something off the market. A tender process, such as a request for bids (RFP) or a request for information (RFI), may be required (RFI).

In general, if highly standardised capabilities are required (for example, payroll, appointment scheduling, and electronic point of sale), it is typically preferable to buy an off-the-shelf system for these so-called "systems of record" or "systems of distinction." The systems are known as "systems of innovation" and are more likely to be suitable to a custom construction when they have requirements that are unique to the industry or organization or give capabilities that provide a competitive edge.

Business analysts and UX designers may collaborate throughout the design stage to develop wireframes or mock-ups of the system's appearance. Technical architects and solution designers may begin to build the system's architecture and make tech stack, hosting, and programming language decisions while keeping in mind the organization's present skillset and vendors in mind.

The design phase's major outputs will vary every system, but they are likely to include wireframes, a systems architectural diagram, a tech stack choice, and an indication of resourcing skills necessary.


Software developers translate the output of the "requirements" and "design" phases into usable software in the build phase. This might include creating front ends, back ends, databases, microservices, and a variety of other components.

The software will be built to provide the functionality specified in the requirements document, and the best projects will maintain end-user engagement throughout this phase to ensure that the things being built are closely aligned with the originally stated requirements, as what is built can sometimes deviate from this.


Test analysts will execute a variety of validation tests on the program throughout the testing process, including performance testing, load testing, and exploratory manual testing. The major goal is to make sure that the work done during the build phase is of a high enough quality to withstand the demands that will be placed on the system under normal operating settings, as well as to figure out what happens when those criteria are surpassed.

User acceptance testing may now begin to validate that the system's behavior meets the stated expectations from the requirements collecting phase, while tight collaboration between users and the development team during the build phase can assist to minimize rework and eliminate surprises.


The program is put into the required production environments and platforms where it will be run during the deployment phase. These environments can be actual servers in a company's data center, or a cloud hosted platform, which is becoming more popular.

End-user training is expected to commence at this phase to ensure that everyone understands how to use the new system, and any data transfer from the prior legacy system will be finished to avoid the need for "double keying."

Discussions with the teams that will be supporting and sustaining the system in its "business as usual" condition should have already begun, and these teams should be taken into account throughout the training phase to ensure that they will be able to support the system once the project team has disbanded.


The system is handed over to the team that will support it for the rest of its life at the company during the maintenance phase. For service desk operators to know how to send user support inquiries to the appropriate team, proper documentation and helpfiles will need to be developed.

Enhancements and changes to the system may be made over time, for example, if new requirements are discovered or if external factors such as regulatory changes occur, and the approach for doing so must be considered, i.e., whether internal resources will be retained to make such changes, or will the changes be farmed out to an external provider on an ad hoc basis.

Check out our post for additional information on the software development lifecycle and how to expand on it to guarantee security is built-in throughout: [Practical Guide] Secure Software Development Lifecycle.

Software Testing Life Cycle (STLC)

Software Testing Life Cycle (STLC) is a method for ensuring that adequate thorough, rigorous tests are implemented from the beginning of a system's development to its end. It is divided into five phases, as follows −

Analysis of Requirements

The testing team examines the business requirements document (BRD) prepared during the SDLC requirements phase in order to identify the important outcomes and capabilities required from the new system during the requirements analysis phase.

The testing team will go over the BRD with key stakeholders and business analysts to ensure that everyone understands what is being created and how it should work. They should also take into account the system's business criticality as well as any applicable regulatory requirements to ensure that any compliance needs are met.

Test Preparation

The testing team will be able to plan how they will implement their tests once the functionality and consequences are known. They'll create a test strategy document for the project, outlining how they'll employ the different technologies available to them, including manual, automated, integration, and unit tests. They may begin to make a list of the exact test cases or scripts that will need to be written in order to verify that the system is thoroughly tested.

Development of Tests

After the high-level test cases and methodologies have been defined, work on fleshing out the test scripts with more information such as the individual user experiences that will need to be evaluated, both from a happy path and an edge case viewpoint, may begin.

Setup of the Test Environment

The test team may start building an appropriate test environment, distinct from the production and development environments after a workable version of the system has been established. In this test environment, they'll make sure they've built up the right user profiles, with the right user login credentials and enough test data to run their scripts.

Execution and Closure of Tests

Finally, after a stable environment has been established, the test team executes the scripts they prepared and reports their findings to the project team and stakeholders. This and other steps may need to be done several times as the project team deals with the results and then retests them.

SDLC vs. STLC: What's the Difference?

The following table highlights the major differences between SDLC and STLC.

TitleSoftware Delivery Lifecycle is a term used to describe how software is delivered.Lifecycle of Software Testing
SummaryConcerned about developing softwareConcerned about software testing
ObjectiveAscertain that software systems are well-built.Ensure that software systems are well tested.
PhasesRequirements Design, Build, Test, Deploy, and MaintainAnalyze the requirements Planning the development of tests Execution and closure of the environment
Involved PeopleWhole project teamTesters/QA Engineer
OutputSystem of software that can be usedSystem of software that has been thoroughly tested


  • To summarize, the SDLC and STLC are two distinct but complimentary procedures that must both be addressed while developing a new system.

  • SDLC is involved with the development of new systems, whereas STLC is exclusively concerned with their testing.

  • SDLC is a linear process that ensures you design and construct the proper system, but the STLC is a technique that allows you to test what you've developed thoroughly.

  • Although STLC is a stand-alone approach to testing, this does not rule out the inclusion of quality assurance in the SDLC. STLC is not a replacement for excellent design or a remedy for poor development; quality should be embedded into software rather than "tested out of it."

  • Any successful new software system will almost certainly include the SDLC and STLC.

  • SDLC provides for the delivery of well-defined software projects in a staged and systematic manner. STLC enables such initiatives to be thoroughly tested to verify that they are efficient, dependable, and useful.

Updated on: 26-Nov-2021

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