This is the approach in which testing is performed earlier in the lifecycle. It can be said like test early and often.
Type of shift left testing
There are four types of shift left testing.
1-Traditional Shift left testing.
2-Incremental Shift left testing.
3-Agile shift left testing.
Model-basedshift left testing.
Traditional Shift left Testing
Traditional shift testing is a classic V-model testing in which unit testing and integration testing is emphasized more than the acceptance and system level testing.
Incremental Shift left Testing
Below is the mentioned figure, there are several projects with complex software-reliant systems which
breaksinto smaller increments having short durations. The shift left is indicated by the red dashed arrows because parts of single, large waterfall V model testing (grey model) are shifted left to become increments of corresponding varieties of testing. When each increment is delivered to the customers the testing and developmental testing shift to the left.This shift testing is popular while testing large complex systems specifically those incorporating significant amounts of hardware.
Agile Shift left Testing
Below given figure defines the agile shift left testing, this is used for the projects which have numerous short durations a.k.a Sprints.These vs also get modified id one or more early suits are used to block out the basic requirements of if test-first and TDD are being performed. Here shift occurs because the types of testing on the right side are tiny as compared to the left side which is larger(s) and they get replaced by the larger one.Agile testing is restricted to developmental testing and does not include operational testing once the system is placed into operations.Transitions here is an ongoing process
Model-based shift left Testing
The previous form of shifting testing was concentrated at the earlier stage of the development cycle.WAiting until software exists to being testing, however, largely and unnecessarily limits the use to testing uncovering coding defects.Many defects are introduced in requirements itself. In the below figure the model testing moves to the left of Vs by testing requirements, architecture and design models.