Regression Preventer looks at a change you're about to make and identifies which existing test cases it could break — before you write or ship the code. It produces a short "guard rail brief": the specific behaviours your change is at risk of regressing, drawn from your Testmo repository.
What it does
Most regressions aren't in the code you're changing — they're in the behaviour that depends on it, often in places you weren't thinking about. Regression Preventer surfaces that blast radius up front:
- You describe the change (a feature, a refactor, a fix).
- The skill finds the test cases that touch the affected behaviour.
- It flags the cases most at risk and explains why each one could be affected.
- You get a guard rail brief you can use to shape the implementation and target your testing.
When to use it
- Before starting a change in a well-tested or high-risk area.
- When refactoring shared code that many features rely on.
- When you want a focused re-test list instead of re-running everything.
- As a companion to Change Evaluator: Regression Preventer tells you what's at risk; Change Evaluator predicts the actual pass/fail outcome once the change exists.
How to run it
With the Testmo skills installed (see the hub article), describe the change and ask for the risk brief. For example:
I'm about to change how discount codes are applied at checkout.
Which of our test cases could this break?The skill uses Semantic Search to find the cases connected to that behaviour and reasons about which ones your change puts at risk. It's a read capability, so a read-only connection is enough.
What you get back
A guard rail brief listing the test cases your change could regress, each with a short explanation of the risk — so you can build the change defensively and re-test exactly what matters, rather than discovering the breakage later.