Add unit tests for price snapshot helper computing percentage change between two snapshots

[Chucks1093]

Summary

The price snapshot helper that computes percentage change between two snapshots is used in the creator list and price alert paths but has no unit tests. Tests should cover positive change, negative change, zero change, and a zero starting price edge case.

Scope

• Test positive change: price moves from 100 to 150 → returns 50.00
• Test negative change: price moves from 200 to 100 → returns -50.00
• Test zero change: same price → returns 0.00
• Test zero starting price: returns null or a sentinel to signal undefined percentage

Acceptance Criteria

• Positive change returns correct percentage
• Negative change returns correct negative percentage
• Zero change returns 0.00
• Zero starting price handled without division-by-zero error

ETA: 12 hours

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Coordinate on Telegram

[jchinedu]

Hi! I'd like to work on this issue.

I'm a Backend/Full Stack Software Engineer with experience building and testing production applications using TypeScript, Node.js, Java (Spring Boot), PostgreSQL, and modern backend development practices. I place a strong emphasis on writing reliable, well-tested code and understand the importance of unit tests in preventing regressions and documenting expected behavior.

After reviewing this issue, I understand the goal is to add comprehensive unit tests for the price snapshot helper, covering positive and negative percentage changes, zero change, and the zero starting price edge case to ensure the helper behaves correctly under all expected scenarios. I'll keep the implementation focused on the requested test coverage, verify the existing behavior is preserved, and ensure the full test suite continues to pass before submitting the PR.

I'm comfortable contributing to existing codebases, following project conventions, and incorporating review feedback promptly. I'd appreciate the opportunity to work on this issue.