Keep seeded PRNG output strictly below 1 in checkout-pricing test

[stefan-burke]

Summary

Follow-up from the PR #1729 review (item #5 in TODO.md). The seeded PRNG in test/lib/checkout-pricing-consistency.test.ts divided by 0x7fffffff (2³¹−1), so rand() returned exactly 1 when seed === 0x7fffffff. That would let pick index one past the array (undefined) and randInt return hi + 1, producing invalid generated test data.

Changes

• makeRng's rand() now divides by 0x80000000 (2³¹), so the output is always in [0, 1).
• Removed the corresponding follow-up entry from TODO.md.

Note this shifts the seeded sequence (i.e. which random cases the property test explores); the test asserts an invariant (public ↔ webhook re-price identically) rather than hardcoded outputs, so it still passes.

Verification

• deno task lint:ci on the file — clean.
• deno check — passes.
• test/lib/checkout-pricing-consistency.test.ts — passes (14 steps).

🤖 Generated with Claude Code

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Generated by Claude Code

Summary by CodeRabbit

• Tests

  • Improved deterministic pricing consistency tests to ensure generated random values remain within the expected range, preventing boundary-related calculation issues.

• Documentation

  • Updated development follow-up notes to clarify expected command-line error handling for incomplete value flags.
  • Removed a completed random-number edge-case item from the follow-up list.

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Review details

⚙️ Run configuration

Configuration used: Organization UI

Review profile: ASSERTIVE

Plan: Pro Plus

Run ID: cd16d7c2-0cbe-4e99-bae3-cf723634fe7a

📥 Commits

Reviewing files that changed from the base of the PR and between 595f9e0 and 7b45d35.

📒 Files selected for processing (1)

• test/shared/payment-signature.test.ts

📝 Walkthrough

Walkthrough

The deterministic test PRNG now normalizes values to the half-open range [0, 1). The TODO list documents a missing-value CLI error and removes the resolved seeded PRNG follow-up.

Changes

PRNG and code-quality follow-ups

Layer / File(s)	Summary
Normalize deterministic PRNG output test/lib/checkout-pricing-consistency.test.ts	Changes the RNG divisor to 0x80000000 and documents the [0, 1) boundary behavior.
Update code-quality follow-ups TODO.md	Specifies fail-fast handling for missing recognized flag values and removes the seeded PRNG follow-up.

Estimated code review effort: 2 (Simple) | ~10 minutes

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly describes the main change: fixing the seeded PRNG in the checkout-pricing test to stay below 1.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch claude/biome-ts-scripts-exclusion-jp4auc

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@test/lib/checkout-pricing-consistency.test.ts`:
- Around line 121-124: Update the identical LCG rand() implementation in
payment-signature.test.ts to divide by 0x80000000 instead of 0x7fffffff,
ensuring rand() remains in [0, 1) and pick() cannot index past the array.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: ASSERTIVE

Plan: Pro Plus

Run ID: 64436e5b-4dfb-4827-8ed4-d141ea27e62e

📥 Commits

Reviewing files that changed from the base of the PR and between 41a9982 and 595f9e0.

📒 Files selected for processing (2)

• TODO.md
• test/lib/checkout-pricing-consistency.test.ts

💤 Files with no reviewable changes (1)

• TODO.md