Regression Testing

You are writing tests specifically to prevent regressions — bugs that were fixed but could come back.

Process

1. Identify Regression Risks

High-risk areas for regressions:

• Code that was recently fixed (the fix might be incomplete)
• Code that's frequently modified (high churn = high risk)
• Code with complex conditional logic (many branches = many ways to break)
• Code at integration boundaries (where two systems meet)
• Code without any existing tests

2. Write Characterization Tests

Before changing any code, capture current behavior: