Kent Beck Code Review Lens
"Make the change easy, then make the easy change."
Four Rules of Simple Design (in priority order)
- Passes tests — Tests pass
- Reveals intention — Names and structure reveal intent
- No duplication — Eliminate idea-level duplication
- Fewest elements — Minimal components
Review Checklist
File Size
# Detect 500+ line files (God Object candidates)
find core/ -name "*.py" -exec wc -l {} + | sort -rn | head -20
File size identifies inspection candidates, not a split requirement. Trace
responsibilities, callers, and reasons to change before proposing extraction.
Do not carry a dated file-size snapshot forward as current implementation status.
Method Size & Complexity
Inspect the actual function and its callers. Function length, nesting, and
branch counts do not by themselves justify a Strategy, dispatch table, or new
module. Prefer an early return or an existing helper when it resolves the
identified failure without obscuring domain behavior.
Reveals Intention
| Anti-pattern | Improvement |
|---|
def process(data) | def score_analyst_response(response) |
result = fn(x, y, z) | Use meaningful variable names |
# This function does X | Reveal through function name, remove comment |
magic number 0.7 | CONFIDENCE_THRESHOLD = 0.7 |
No Duplication
Detect idea-level duplication (not just copy-paste but missing abstractions):
Trace repeated decisions through their shared owner. Unify behavior that must
change together; keep similar-looking paths separate when their contracts differ.
Neither repetition count nor structural similarity alone requires a factory,
Protocol, or generic abstraction.
Fewest Elements
| Unnecessary Element | Criteria |
|---|
| Unused parameters | Wrappers that only pass **kwargs |
| ABC with single implementation | Check the substitution contract; a concrete class may be sufficient |
Empty __init__.py | Check package, distribution, discovery, and import contracts before removal |
| Unused imports | Auto-detected by ruff F401 |
Scope and Verification
A review does not authorize refactoring. Follow the
workflow for requested changes and the
deletion gate
before removing code, tests, or package files. Use
verification gates for
targeted checks and evidence reuse. Report concrete findings with current
file/line evidence; no finding is preferable to a speculative simplification.