Difference between SDLC and STLC

SDLC, software/system development lifecycle, refers to the various phases involved in the software development process, including gathering requirement, designing, implementation, testing, deployment, and finally maintenance.


Whereas STLC, or software/system testing lifecycle, describes all the activities performed during the testing process of a software product. STLC focuses more on testing, instead of the whole development process of a software product. The foundation of STLC is a developed software product instead of a business document which outlines all the requirements of customers/clients. It is common to see that STLC is contained in SDLC.

Below is a really good table which describes the similarities and differences between these two:

S. No. Phase SDLC – Software Development Lifecycle STLC – Software Test Lifecycle
1 Requirements Gathering Requirements gathering is done by the business analyst. Development team analyze the requirements from the design, architecture & coding perspective. Testing team also reviews & analyzes the requirements, and identifies the testing requirements, e.g. what types of testing will be required. The team will review the requirements for logical functional relationship between various features / modules, to ensure that any gaps can be caught at an early stage.
2 Design Technical architect works for the high level & low design of the software to make sure that high level and low design are met. The business analyst works for the UI design of the application Here, test architect, generally the test lead/manager, does the test planning, and identifies high-level testing points. Basically, requirement detailing is done in this phase.
3 Coding or development Development team does the actual coding based on the designed architecture. Testing team writes the detailed test cases.
4 Testing In SDLC, actual testing is carried out in this phase. It includes unit testing, integration testing & system testing etc.. Test Execution and bug reporting, manual testing, automation testing is done, defects found are reported. Re-testing and regression testing is also done in this phase.
5 Deployment Application is deployed on production environment for real end users. Final testing and implementation are done in this phase and the final test report is prepared.
6 Maintenance Basically, it includes posting production and deployment support, and follow-up with enhancements.  Test team here will do updating & maintenance of test plans, test case required for the testing of support requests & enhancements as a part of maintenance.

Which phase of SDLC we write test case

Within the loop of SLDC, we write test cases and execute the testing stuff in the phase of “Testing”. For STLC, the test cases will be written when then phase of “Coding/Development”.

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