test(invoice-token): cross-contract integration test suite for escrow-triggered burn-on-settlement callback

[chizzy192]

Context & Problem Statement

During invoice escrow settlement, the escrow contract invokes burn or burn_from on the InvoiceToken contract to retire the tokenized invoice representations in exchange for distributed payout capital. While unit tests verify token burning in isolation, end-to-end integration tests proving cross-contract authorization, allowance consumption, and post-settlement transfer unlock are needed.

This issue introduces a MockSettlementEscrow contract harness in contracts/invoice-token/src/integration_test.rs to validate the complete escrow-to-token settlement flow.

Architectural Motivation & Technical Requirements

• In contracts/invoice-token/src/integration_test.rs:
  • Implement a MockSettlementEscrow contract and setup harness.
  • Implement integration tests covering:
    • Happy-path burn_on_settlement and burn_from_on_settlement.
    • Allowance deduction and verification on burn_from.
    • Failure paths: InsufficientBalance, InvalidAmount, InsufficientAllowance, AllowanceExpired, Paused.
    • Verify that after full settlement, token transfers are unlocked and residual balances persist accurately.
• Assert emitted event logs on both contracts.

Acceptance Criteria

• Mock settlement escrow harness implemented.
• Happy path and all 5 negative error paths covered.
• Post-settlement transfer unlock explicitly verified.
• cargo test -p invoice-token passes.

Target Branch: dev
Estimated Effort: 5–12 hours | Delivery: 3–5 days
Difficulty: Medium

[Engr-Able]

@Engr-Able has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

Hello Maintainer, I’ve read through the issue description and have a clear understanding of the expected outcome. I’d be pleased to take on this task and contribute a quality solution to the project.

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[neyij]

@neyij has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

hi, i would like to work on this.

ℹ️ Repo Maintainers: To accept this application, review their application or assign @neyij to this issue.

[drips-wave]

Congratulations, @neyij! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on August 31, 2026.

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