Shift left testing is testing early in the Software Development Life Cycle (SDLC). It is called that because, as you look at a project timeline, testing moves left to earlier dates in the project. Testing early in the SDLC helps catch bugs that would be costly to fix at later stages. It is best to involve the test team as early as possible, even in the requirements gathering stage of the SDLC, to identify potential pitfalls and testing concerns.