self sub test

[thedavidmeister]

Motivation

Solution

Checks

By submitting this for review, I'm confirming I've done the following:

• made this PR as small as possible
• unit-tested any new functionality
• linked any relevant issues or PRs
• included screenshots (if this involves a front-end change)

Summary by CodeRabbit

• Tests
  • Added a new test case for self-subtraction to expand coverage of decimal float subtraction scenarios.
• Chores
  • Updated gas snapshot with minor metric adjustments for several subtraction tests.

[coderabbitai]

Walkthrough

Adds a new subtraction self-test to LibDecimalFloatImplementationSubTest and updates corresponding gas snapshot metrics for several subtraction tests, including the new case. No production code or public API changes.

Changes

Cohort / File(s)	Summary
Gas snapshot updates /.gas-snapshot	Updated gas metrics for three existing subtraction tests and added a new entry for testSubSelf.
Subtraction tests test/src/lib/implementation/LibDecimalFloatImplementation.sub.t.sol	Added testSubSelf(int224,int32) to verify subtracting identical operands yields zero coefficient; no other test logic changes.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~3 minutes

Possibly related PRs

• sub #97: Modifies the same LibDecimalFloatImplementationSubTest with subtraction-focused tests, including adjustments around testSubOneFromMax.

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📜 Recent review details

Configuration used: CodeRabbit UI
Review profile: ASSERTIVE
Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 1f50603 and 00cd471.

📒 Files selected for processing (2)

• .gas-snapshot (1 hunks)
• test/src/lib/implementation/LibDecimalFloatImplementation.sub.t.sol (1 hunks)

🧰 Additional context used

🧠 Learnings (1)

📓 Common learnings

Learnt from: thedavidmeister
PR: rainlanguage/rain.math.float#96
File: test/src/lib/implementation/LibDecimalFloatImplementation.maximize.t.sol:15-29
Timestamp: 2025-08-11T14:32:50.439Z
Learning: In test code for the rain.math.float repository, redundant checks may be intentionally kept for clarity and documentation purposes, even when they could be simplified. The maintainer (thedavidmeister) prefers explicit assertions in test code to make the test's intent clear to future readers, prioritizing readability over conciseness.

⏰ Context from checks skipped due to timeout of 90000ms. You can increase the timeout in your CodeRabbit configuration to a maximum of 15 minutes (900000ms). (7)

• GitHub Check: git-clean
• GitHub Check: rainix (ubuntu-latest, rainix-sol-test)
• GitHub Check: rainix (ubuntu-latest, test-wasm-build)
• GitHub Check: rainix (ubuntu-latest, rainix-rs-static)
• GitHub Check: rainix (ubuntu-latest, rainix-rs-test)
• GitHub Check: rainix (ubuntu-latest, rainix-sol-static)
• GitHub Check: rainix (macos-latest, rainix-rs-test)

🔇 Additional comments (3)

test/src/lib/implementation/LibDecimalFloatImplementation.sub.t.sol (1)

68-73: LGTM! Well-designed self-subtraction test.

The test correctly verifies that subtracting any value from itself results in zero coefficient. The implementation is clean, follows established patterns in the test suite, and appropriately silences the unused exponent variable.

.gas-snapshot (2)

201-201: New test gas measurement looks reasonable.

The gas usage for testSubSelf (μ 5346, ~ 5449) is consistent with other simple subtraction tests in the suite.

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200-200: No implementation changes detected – gas increase likely due to toolchain upgrade

I reviewed the production code and test files and found:

• LibDecimalFloatImplementation.sub in src/lib/implementation/LibDecimalFloatImplementation.sol is unchanged
• testSubOneFromMax in test/src/lib/implementation/LibDecimalFloatImplementation.sub.t.sol is new, with no modifications to existing logic
• The checkSub helper is unchanged

Since we only added a new pure test, an ~18% gas bump almost certainly stems from an external change (compiler, EVM, or Foundry version) rather than our contract logic. Please verify:

• That your Solidity compiler and Foundry (forge) versions are consistent with previous runs
• If versions did change, either pin them or regenerate/update the .gas-snapshot to reflect the new baseline

✨ Finishing Touches

🧪 Generate unit tests

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch 2025-08-11-sub-self

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