test: implement unit and integration tests for all contracts

[DeFiVC]

Summary

• Implement 8 learn-token unit tests (metadata, mint, transfer, insufficient balance, claim_reward, double claim, high score, allowance)
• Implement 8 credential-nft unit tests (low score rejection, valid mint, duplicates, get credentials, revoke, double revoke, nonexistent, ID increment)
• Implement 12 progress-tracker unit tests (enrollment, modules, quizzes, eligibility, low scores, double enroll/module/quiz, score max, not enrolled, course creation, mismatch)
• Wire up integration fixtures with real contract registration replacing placeholder addresses
• Complete 5 token flow end-to-end tests (reward flow, double claim, multiple quizzes, transfer, supply consistency)
• Complete 6 credential flow end-to-end tests (full flow, public verification, multiple credentials, revocation, metadata URI, issuance timestamp)

Closes #1, #2, #3, #4

Test plan

cd chainlearn-contracts
cargo test --package learn-token --test token_tests
cargo test --package credential-nft --test credential_tests
cargo test --package progress-tracker --test progress_tests
cargo test --test token_flow
cargo test --test credential_flow

[DeFiVC]

Review Summary

Solid implementation. All 28 unit tests and 11 integration tests properly wired up with real contract registration.

What's Good

• setup_token/setup_contract helpers match inline test patterns exactly
• All #[should_panic] annotations have correct expected strings
• Integration fixtures register all 3 contracts (no placeholder addresses)
• complete_full_course helper is reusable across integration tests

Action Needed

• Branch is behind main — rebase before merge
• No CI configured yet — verify locally with cargo test

[DeFiVC]

Review: PR #5 — Implement unit and integration tests for all contracts

Verdict: APPROVE — All 28 unit tests and 11 integration tests are correctly implemented. Code matches the inline test patterns and contract behavior.

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1. Linked Issue Coverage

• ✅ Issue Implement unit tests for learn-token contract (tests/unit/token_tests.rs) #1 (learn-token unit tests) — linked in closingIssuesReferences, fully covered
• ⚠️ Issues Implement unit tests for credential-nft contract (tests/unit/credential_tests.rs) #2, Implement unit tests for progress-tracker contract (tests/unit/progress_tests.rs) #3, Implement integration tests: fixtures + token/credential flow tests #4 — PR body claims "Closes Implement unit tests for learn-token contract (tests/unit/token_tests.rs) #1, Implement unit tests for credential-nft contract (tests/unit/credential_tests.rs) #2, Implement unit tests for progress-tracker contract (tests/unit/progress_tests.rs) #3, Implement integration tests: fixtures + token/credential flow tests #4" but only Implement unit tests for learn-token contract (tests/unit/token_tests.rs) #1 is auto-linked. Issues Implement unit tests for credential-nft contract (tests/unit/credential_tests.rs) #2-4 will need manual closure after merge.

2. Code Quality — Unit Tests

token_tests.rs (8 tests) — ✅ All correct

• setup_token helper matches inline tests at lib.rs:244-257 exactly
• Uses Symbol::new instead of symbol_short! — functionally equivalent for these short strings
• test_claim_reward_proportional_minting: correctly verifies 80 * 100 = 8000 and checks total_supply
• test_transfer_from_with_allowance: correctly verifies allowance decreases from 500 to 200 after 300 transfer

credential_tests.rs (8 tests) — ✅ All correct

• setup_contract matches inline tests at lib.rs:97-103
• test_mint_requires_passing_score: #[should_panic(expected = "score 40 below minimum threshold 50")] matches mint.rs:33-36 format string exactly
• test_prevent_duplicate_credentials: matches mint.rs:42 panic message
• test_nonexistent_credential_invalid: correctly tests ID 999 without needing a course (mint doesn't validate course existence)

progress_tests.rs (12 tests) — ✅ All correct

• setup_contract + create_test_course match inline tests at lib.rs:290-306
• All 6 #[should_panic] strings verified against source:
  • "already enrolled" → lib.rs:88
  • "module already completed" → lib.rs:127
  • "quiz already submitted" → lib.rs:199
  • "score exceeds maximum" → lib.rs:185
  • "not enrolled" → lib.rs:121 (.expect())
  • "module_ids length must match total_modules" → lib.rs:48
• test_eligibility_fails_with_low_quiz_scores: correctly uses scores 30+40 (avg=35 < 50 threshold)

3. Code Quality — Integration Tests

fixtures.rs — ✅ Properly wired

• setup_chainlearn_env registers all 3 real contracts (no placeholder addresses)
• create_sample_course takes &ProgressTrackerClient and creates course with 3 modules
• complete_full_course enrolls → completes 3 modules → submits 2 quiz scores

token_flow.rs (5 tests) — ✅ All correct

• test_end_to_end_reward_flow: full enroll → modules → quiz → claim → verify balance
• test_learner_to_learner_transfer: claims 10000, transfers 3000, verifies both balances
• test_total_supply_consistency: two learners claim independently, verifies sum

credential_flow.rs (6 tests) — ✅ All correct

• test_end_to_end_credential_flow: uses complete_full_course helper, mints with avg score 80
• test_public_verification: mints without course creation — correct since mint_credential doesn't require it
• test_credential_has_issuance_timestamp: verifies issued_at > 0 (set from env.ledger().timestamp())

4. CI Status

No CI checks configured for this repo. Tests can only be verified locally with cargo test.

5. Merge Conflicts

• mergeable: MERGEABLE — no conflicts
• mergeStateStatus: BLOCKED — branch is behind main, needs rebase

6. Minor Nits (non-blocking)

• Doc comments were removed from tests (e.g., /// Test that... lines). The inline tests don't have them either, so this is consistent, but they were useful for readability in the standalone test files.
• No symbol_short! usage — Symbol::new is fine but slightly less idiomatic for short literals.

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What's Good

• Setup helpers (setup_token, setup_contract, create_test_course) are consistent across unit and integration tests
• All #[should_panic] expected strings verified byte-for-byte against contract source
• Integration fixtures properly register real contracts instead of using placeholder addresses
• complete_full_course helper is reusable and correctly drives the full enrollment→completion→eligibility flow
• Tests cover happy paths, error paths, and edge cases (double claims, duplicates, insufficient balance, score limits)