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This blog was originally posted on July 18, 2016 and was updated with revised content on August 21, 2020.

The concept of "shift left" is a key component to successful DevOps, continuous integration, and continuous deployment initiatives. To "shift left" simply means to conduct more testing earlier in the value stream (i.e. move it to the "left" on a left-to-right stream representing the continuous journey from planning, development, to deployment and beyond. The goal of shifting left is to deliver applications faster with less effort/cost).

The Relationship Between Shift Left Testing and DevOps Automation
What is the point of doing a leftward shift? There are several good reasons for organizations to enable earlier testing in the value stream:

Defects become increasingly expensive to fix the later they are discovered in the application lifecycle. The well-known chart from IBM Systems Sciences Institute on the relative costs of such bugs demonstrated that a flaw discovered during testing costs 15 times as much as one found during design, while one revealed during maintenance costs a staggering 100 times as much.