Pharo Refactor

Pharo refactor loop (live image, via the genie MCP tools)

Refactoring = change structure without changing behavior. The proof that behavior is unchanged is a green test suite before AND after. All reads and writes go through the genie MCP tools; there are no files. Change code only via define_method / define_class / rename_class / remove_method / eval, and read every change back to confirm it.

Loop

1. Green baseline. Run run_test on the relevant class/package. If the code you're about to touch has NO test coverage, STOP and write characterization tests first (use the pharo-tdd skill) — you cannot refactor safely without a safety net.

2. Map impact. Before any rename/move/extract, find every caller and implementor:

   • search_references / search_references_to_class — who uses it
   • search_implementors — who else defines this selector
   • search_methods_like — similar code that may need the same change Make a list. Every item gets updated in this same session.

3. One small change. Make a single structured edit. Read changed methods back with get_method_source.

4. Re-test. Run run_test (class, then package). Green → keep going. Red → the trace shows what broke; fix or revert this one step before moving on. Never batch unverified edits.

5. Repeat steps 3–4 in small increments until the cleanup is complete.

6. Done. Persist with save_image gated on the test package. Summarize the before/after shape.

Common moves

• Rename class: use rename_class — it updates every code reference and symbol literal via the refactoring engine. It does NOT touch string literals, so fix stringly-typed names by hand; and in a test that renames a class, refer to the old name as 'Foo' asSymbol, never #Foo, or the test rewrites its own assertion and self-mangles.
• Remove method: remove_method. Remove class: remove_class.
• Rename method: install the new selector via define_method, repoint every sender (from search_references), then remove_method the old one.
• Extract method: add the new helper, call it from the original, re-test.

Rules

• Behavior-preserving only. If a test changes meaning, that's a feature change — do it under pharo-tdd, not here.
• Small steps, tests between each. A long unverified refactor is a bug factory.
• Modern class API only (ShiftClassInstaller / define_class).