build-discipline

Use test-first vertical slices to prevent scope creep during multi-file feature implementation. Anchor each slice to the design spec, implement the simplest working change, and use explicit Changed/Not touched/Concerns summaries to guard against speculative abstractions.

Debug a root cause regression fix by reproducing the failure, localizing the failing layer, adding a failing test proving the bug, and applying the smallest code change that removes the root cause while preserving regression coverage.

Structure a test-first software build workflow by writing or extending a failing test before any code changes, implementing the working fix, and running targeted then broader CI verification after each slice to ensure safer changes.

Large code changes become hard to debug during iteration because they drift away from the spec and introduce speculative abstractions. Enforcing small, evidence-driven, test-first vertical slices keeps increments manageable and isolated.

Yes, test-first development works for repairing existing features by requiring a failing test that reproduces the bug before applying the smallest fix. This maintains maintainability and prevents scope-creep during the verify-fix cycle.

Avoid vertical slices when the task lacks a clear spec or scaffolding scope to anchor increments. Without an anchor, the test-first approach cannot enforce maintainability or prevent speculative architecture changes effectively.