Defect Slippage

What is Defect Slippage?

Defect slippage occurs when a defect that should have been caught in an earlier testing phase is instead found in a later phase (or worse, after release in production).

Examples of Defect Slippage

• A defect that should have been caught during unit testing is instead found during system testing.
• A defect missed throughout all testing phases is found by real users after release.

Why Defect Slippage Matters

High defect slippage indicates gaps in the testing process at earlier stages, and is used as a key quality metric to evaluate and improve the effectiveness of each testing phase.