Incremental shift left testing is a widely adopted method that starts software testing earlier in the development cycle – shifting it to the left on the timeline -- and breaks complex development down into smaller pieces that build upon each other.
Incremental shift left testing is most common for developing large, complex systems with specific hardware integration. Testing incrementally makes it possible to ensure that each segment of the program is functional before anything else is added.
Shift left testing is designed to catch problems earlier in the development cycle, leaving time available to correct issues that are found. Broken into increments, testing can be further accelerated and better organized. Since development can often be conveniently broken down into separate packages, the elements of a program can be tested by different teams at the same time. Alternatives to the incremental approach include traditional shift left testing, Agile/DevOps and model-based shift left testing.