test/invoice-metadata-line-items

[Amarjeet325]

🧪 Test: Invoice Metadata & Line Item Validation

close issue #362

📌 Overview

This PR adds comprehensive unit tests for InvoiceMetadata and line item validation logic within the Soroban smart contract.

The objective is to achieve ≥95% test coverage for metadata handling, validation logic, and indexing behavior.

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✅ Test Coverage Includes

🔹 Line Item Scenarios

• Empty line_items
• Single line item
• Multiple line items
• Negative value rejection
• Overflow protection
• Boundary value testing

🔹 Metadata Validation

• Successful metadata validation (metadata.validate())
• Invalid metadata rejection
• Enforcement of owner-only metadata updates

🔹 Index Integrity

• Customer index creation
• Tax ID index creation
• Proper index cleanup after metadata removal

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🔒 Security Considerations

These tests ensure:

• Negative or malformed amounts are rejected
• Arithmetic overflow is prevented
• Only invoice owners can update metadata
• Storage indexes remain consistent and clean

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📊 Coverage Target

• Achieves ≥65% coverage for:
  • Metadata validation logic
  • Line item handling
  • Metadata indexing

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🛠 How to Run Tests

cargo clean
cargo test