Deliver the refactor with precise coverage limits
See this course’s project requirements
A before/after fictional fee calculator split into pure functions with an executable equivalence suite, clearer names and documented intentional nonchanges.
Keep your working files in your own notebook or software. Save a private description, checklist, and work link in My Proof.
What to include
- Produce a complete valid/rejected behavior contract and intentional-change boundary.
- Retain full finite valid-space coverage and explicitly scoped invalid-case comparisons.
- Create checked validation/subtotal helpers and preserve the public entry contract.
- Produce a domain-name/reference review with unchanged discount and delivery semantics.
- Retain a passing baseline and an expected failing price mutation without altering final pricing.
- Deliver an independently reasoned, repeatable refactor with finite coverage and selected-invalid limits.
Review and revise
Use these criteria to check your work and choose what to improve.
- The implementation or declared simulation follows the supplied contract and retains inspectable original inputs.
- Normal, boundary and rejected cases are recorded with expected versus observed results.
- The changed case has a correct explanation and does not rely on hidden state.
- The project includes source, outputs, instructions and honest tool, privacy and verification limits.
Want more background?
The idea in everyday life
Fictional workshop kits: quantity 1–20, $3 per kit, a 20% member discount on kit subtotal, and $2.50 only for post. Calculations return integer cents. legacy_fee.py and refactored_fee.py must agree on permitted and rejected requests.
The final project shows preserved behavior, improved responsibilities, and repeatable evidence. Equivalence to a legacy implementation does not prove the original business rule is universally appropriate.
Deliver the refactor with precise coverage limits — original worked practice
The final project shows preserved behavior, improved responsibilities, and repeatable evidence. Equivalence to a legacy implementation does not prove the original business rule is universally appropriate.
Fictional workshop kits: quantity 1–20, $3 per kit, a 20% member discount on kit subtotal, and $2.50 only for post. Calculations return integer cents. legacy_fee.py and refactored_fee.py must agree on permitted and rejected requests.
1. Step 1
Run the repair wrapper on the delivered files and retain its exact output.
You should see: 88 refactor cases passed and changed-price mutation detected.
The final project shows preserved behavior, improved responsibilities, and repeatable evidence. Equivalence to a legacy implementation does not prove the original business rule is universally appropriate.
2. Step 2
Review the original stated kit rules independently against representative hand calculations.
You should see: Equivalence and rule reasoning agree in the supplied case.
The final project shows preserved behavior, improved responsibilities, and repeatable evidence. Equivalence to a legacy implementation does not prove the original business rule is universally appropriate.
3. Step 3
Package both modules, both test files, contract, and structure comparison.
You should see: The before/after handoff is reproducible.
The final project shows preserved behavior, improved responsibilities, and repeatable evidence. Equivalence to a legacy implementation does not prove the original business rule is universally appropriate.
4. Step 4
State the finite valid coverage and eight selected invalid cases; do not claim every possible input or future rule.
You should see: A behavior-preserving refactor packet with precise coverage.
The final project shows preserved behavior, improved responsibilities, and repeatable evidence. Equivalence to a legacy implementation does not prove the original business rule is universally appropriate.
What to finish
Deliver an independently reasoned, repeatable refactor with finite coverage and selected-invalid limits.
Watch for this
Confusing behavioral equivalence with independent correctness of every possible business rule.
How can I tell I understand it?
Demonstrate the rule: The final project shows preserved behavior, improved responsibilities, and repeatable evidence. Equivalence to a legacy implementation does not prove the original business rule is universally appropriate. Use the supplied variant to distinguish a changed result from a broken implementation.
Quick knowledge check
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Source & access notes · checked 2026-10-01
Relevant documented module/API behavior inspected during expansion authoring; actual execution evidence is recorded separately. No grant eligibility is established.
Access: Official page retrieved with the web reader on 2026-10-01. Documentation reading does not certify execution in every native tool or browser.
Reuse: Original local practice files, fictional data, worked examples and questions. Concepts paraphrased and linked; source exercises are not copied.
Source & access notes · checked 2026-10-01
Relevant documented module/API behavior inspected during expansion authoring; actual execution evidence is recorded separately. No grant eligibility is established.
Access: Official page retrieved with the web reader on 2026-10-01. Documentation reading does not certify execution in every native tool or browser.
Reuse: Original local practice files, fictional data, worked examples and questions. Concepts paraphrased and linked; source exercises are not copied.
Source & access notes · checked 2026-10-01
Relevant documented module/API behavior inspected during expansion authoring; actual execution evidence is recorded separately. No grant eligibility is established.
Access: Official page retrieved with the web reader on 2026-10-01. Documentation reading does not certify execution in every native tool or browser.
Reuse: Original local practice files, fictional data, worked examples and questions. Concepts paraphrased and linked; source exercises are not copied.
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