%% Last Updated: [[2021-02-14]] %% # Shift-Left Testing - Wikipedia [Readwise URL](https://readwise.io/bookreview/7721657) | [Source URL](https://en.wikipedia.org/wiki/Shift-left_testing) --- ![](https://readwise-assets.s3.amazonaws.com/static/images/article4.6bc1851654a0.png) --- Shift-left testing is an approach to software testing and system testing in which testing is performed earlier in the lifecycle (i.e. moved left on the project timeline). It is the first half of the maxim "Test early and often." It was coined by Larry Smith in 2001. ^145418665 **References:** https://instapaper.com/read/1377523953/15501353 --- insufficient resources being allocated to testing ^145418666 **References:** https://instapaper.com/read/1377523953/15501414 --- > Defects in requirements, architecture, and design remain undiscovered while significant effort is wasted implementing them. > Debugging (including identifying, localizing, fixing, and regression testing defects) becomes harder as more software is produced and integrated. > Encapsulation impedes white-box testing, reducing code coverage during testing.[citation needed] > 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. ^145418667 **References:** https://instapaper.com/read/1377523953/15501416 --- There are four basic ways to shift testing earlier in the life-cycle (that is, leftward on the classic V-model). These can be referred to as traditional shift-left testing, incremental shift-left testing, Agile/DevOps shift-left testing, and model-based shift-left testing. ^145418668 **References:** https://instapaper.com/read/1377523953/15501418 --- Traditional shift-left testing ^145418669 **References:** https://instapaper.com/read/1377523953/15501419 --- Incremental shift-left testing ^145418670 **References:** https://instapaper.com/read/1377523953/15501422 --- Agile/DevOps shift-left testing ^145418671 **References:** https://instapaper.com/read/1377523953/15501427 --- Model-based shift-left testing ^145418672 **References:** https://instapaper.com/read/1377523953/15501435 --- > The previous forms all concentrated on testing earlier in the development cycle. However, they all test after software exists and seek to uncover only implementation defects.[citation needed] > \ > Model-based testing moves testing to the left side of the Vs, by testing requirements, architecture, and design models. This shift begins testing almost immediately, instead of waiting a long time (traditional testing), medium time (incremental testing), or short time (Agile/DevOps) for software to become available to the right side of the Vs. This trend is just beginning. ^145418673 **References:** https://instapaper.com/read/1377523953/15501437 ---