Comparison
Eval-Driven Development vs Regression Testing (LLMs)
Eval-Driven Development and Regression Testing (LLMs) are both common AI/LLM terms but cover different ideas. Here is a quick side-by-side.
When you would reach for Eval-Driven Development
As soon as you have more than one prompt change per week or more than one engineer iterating on the same prompt.
A team's prompt PR template requires: eval set updated if behavior changed, baseline win rate ≥ 50%, no regressions on three named cases.
When you would reach for Regression Testing (LLMs)
As soon as you have repeat bugs or "we fixed that already, didn't we?" moments.
A PR template requires: zero regressions on the 30 must-pass examples; overall win rate ≥ 50%; cost per call within 10% of baseline.
Frequently asked
What is the difference between Eval-Driven Development and Regression Testing (LLMs)?
Eval-Driven Development: Eval-driven development is the LLM analog of test-driven development: you write evals for behavior before changing the prompt or model, and every change is graded against the same eval suite. Regression Testing (LLMs): LLM regression testing is the practice of running every prompt or model change against a fixed set of "must-pass" examples — bug repros, edge cases, known failure modes — to catch quality regressions.
When should I use Eval-Driven Development vs Regression Testing (LLMs)?
As soon as you have more than one prompt change per week or more than one engineer iterating on the same prompt. As soon as you have repeat bugs or "we fixed that already, didn't we?" moments.
Are Eval-Driven Development and Regression Testing (LLMs) the same thing?
No. Eval-Driven Development is evaluation; Regression Testing (LLMs) is evaluation. They are related but address different parts of the AI stack.