Shift-left testing is important because it helpsaims to prevent the following types of harm due to late testing:
* Testers may be less involved in initial planning, often resulting in insufficientInsufficient resources being allocated to testing.
* DefectsUndiscovered defects in requirements, architecture, and design, remainalong undiscovered whilewith significant effort is wasted while implementing them.
* Difficulty [[Debuggingdebugging]] (including identifying, localizing, fixing, and regression testing defects) becomes harder as more software is produced and integrated.
* Reduced [[code coverage]] during testing{{Citation needed|date=October 2017}} as a result of [[Encapsulation (object-oriented programming)|Encapsulationencapsulation]] impedesimpeding [[white-box testing]], reducing [[code coverage]] during testing.{{Citation needed|date=October 2017}}
* A “bow wave” of [[technical debt]] that can cause a project to fail.
* There is less time to fix defects found by testing, thereby increasing the likelihood that they will be postponed until later increments or versions of the system. This creates a “bow wave” of [[technical debt]] that can sink projects if it grows too large.
