[8] As illustrated in the following figure, traditional shift-left moves the emphasis of testing lower down (and therefore slightly to the left) on the right hand side of the classic V model.
The shift-left illustrated by the dashed red arrows occurs because parts of the single, large waterfall V model’s types of testing (shown in gray) are shifted left to become increments of the corresponding types of testing in the smaller incremental V models.
Incremental shift-left testing is popular when developing large, complex systems, especially those incorporating significant amounts of hardware.
As illustrated in the following figure, Agile and DevOps projects have numerous short duration Vs (sprints) in lieu of a single or small number of V as in the previous two examples of shift-left testing.
These small Vs would also be modified if one or more early sprints are used to block out the basic requirements and architecture or if test-first and test-driven development (TDD) are being performed.