Software development life cycle(SDLC) and Software Testing Life cycle(STLC) go parallelly.

SDLC (Software Development Life cycle) STLC (Software Test Life Cycle)
SDLC is Software Development LifeCycle, it is a systematic approach to develop a software. The process of testing a software in a well planned and systematic way is known as software testing life cycle(STLC).
Requirements gathering Requirements Analysis is done is this phase, software requirements are reviewed by test team.
Design Test Planning, Test analysis and Test design is done in this phase. Test team reviews design documents and prepares the test plan.
Coding or development Test construction and verification is done in this phase, testers write test cases and finalizes test plan.
Testing 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.
Deployment Final testing and implementation is done is this phase andfinal test report is prepared.
Maintenance Maintenance testing is done in this phase.