V Model to W Model | W Model in SDLC Simplified

We already discuss that V-model is the basis of structured testing. However there are few problem with V Model. V Model Represents one-to-one relationship between the documents on the left hand side and the test activities on the right. This is not always correct. System testing not only depends on Function requirements but also depends on technical design, architecture also. Couple of testing activities are not explained in V model. This is a major exception and the V-Model does not support the broader view of testing as a continuously major activity throughout the Software development lifecycle.
Paul Herzlich introduced the W-Model. In W Model, those testing activities are covered which are skipped in V Model.
The ‘W’ model illustrates that the Testing starts from day one of the of the project initiation.
If you see the below picture, 1st “V” shows all the phases of SDLC and 2nd “V” validates the each phase. In 1^st “V”, every activity is shadowed by a test activity. The purpose of the test activity specifically is to determine whether the objectives of that activity have been met and the deliverable meets its requirements. W-Model presents a standard development lifecycle with every development stage mirrored by a test activity. On the left hand side, typically, the deliverables of a development activity (for example, write requirements) is accompanied by a test activity test the requirements and so on.

Fig 1: W Model

Fig 2: Each phase is verified/validated. Dotted arrow shows that every phase in brown is validated/tested through every phase in sky blue.
Now, in the above figure,

• Point 1 refers to - Build Test Plan & Test Strategy.
  
• Point 2 refers to - Scenario Identification.
  
• Point 3, 4 refers to – Test case preparation from Specification document and design documents
  
• Point 5 refers to – review of test cases and update as per the review comments.

So if you see, the above 5 points covers static testing.

• Point 6 refers to – Various testing methodologies (i.e. Unit/integration testing, path testing, equivalence partition, boundary value, specification based testing, security testing, usability testing, performance testing).
  
• After this, there are regression test cycles and then User acceptance testing.

Conclusion - V model only shows dynamic test cycles, but W models gives a broader view of testing. the connection between the various test stages and the basis for the test is clear with W Model (which is not clear in V model).
You can find more comparison of W Model with other SDLC models Here.