The SDLC, or software development process, is a methodology that defines the steps of a software development project. There are several stages in the Software Development Life Cycle. (Source: http://study.com/academy/lesson/what-is-a-software-development-life-cycle-definition-examples.html) The Cycle is although known as Waterfall Method or Classic Life Cycle Model (Source: http://www.stylusinc.com/down-to-earth-ideation/the-software-development-life-cycle-sdlc/) SDLC can be dived into the following six phrases (in some cases the sum of phrases is different): (Source: https://www.tutorialspoint.com/sdlc/sdlc_overview.htm)
Each of these phrases produces deliverables. Those deliverables are required by the next phase in the life Cycle. (Cf.: http://istqbexamcertification.com/what-are-the-software-development-life-cycle-sdlc-phases/) If in one of the following phrases a missing deliverable uncovered the Cycle leap to the phrase in which the missing deliverable is located. An other example with different names phases are shown in the following picture (Source: https://www.google.de/imgres?imgurl=http://www.stylusinc.com/wp-content/uploads/2007/12/SDLC.jpg&imgrefurl=http://www.stylusinc.com/down-to-earth-ideation/the-software-development-life-cycle-sdlc/&h=1024&w=1018&tbnid=yw1jp2OCuvxw1M:&tbnh=160&tbnw=159&usg=__PBkFe4-TGinsR5GdMRIrPoOw6iY=&vet=1&docid=TehlUK46z0dIxM&client=firefox-b&sa=X&ved=0ahUKEwjZnsiO2LLTAhWH1SwKHR-wAm4Q9QEILDAA):
The focus in this phase is to create a Requirement Specification document. Functional and non-functional requirements and may some use cases are located in this document. The document is the basis for an agreement between the customer and the supplier. It is very important that the requirements are clear and both sides, customer and supplier, has the same view of each requirement. After the document exists the project manager will be able to create a project management plan with costs, time, quality measures.
In this phase the software engineering is designed. For example, UML, Use Case Diagram and sequence Diagram will be modelled to make sure the requirements from the customer can transformed into source code correctly. The Software Test Team can now start to create a Test plan for the feature.
In this phase the Software will be coded. In most Software development projects, the Team is coding independent a short part of the whole source code. It is important that the Team is using the same notation. Frequently, often daily, the Team is coming together and are talking about the progress of the project. It is although important that the source code will be documented. After a running Software the test phase could be started.
After the software code is developed it is tested against the requirements which has been located in the first phase. (Cf.: http://istqbexamcertification.com/what-are-the-software-development-life-cycle-sdlc-phases/) You can not test that you can not measure. Thereof for each Test case some expected values have been defined before the Test can start.
If the product has been successfully tested the Software will be delivered / deployed to the customer. (Source: http://istqbexamcertification.com/what-are-the-software-development-life-cycle-sdlc-phases/) The first customers are often used for beta testing. These customers will report bugs and feature requests to the engineering team. After all critical bugs are fixed the product will be released finally.
After the product has successfully released the Software is still not free from errors. Upcoming bugs has to been fixed. Some kind of Software needs frequently security updates our other kinds of maintenance to run.
Often the first two phases are merged into on phase which could be named Planning.