test: LoanPay regression tests for impaired overdue loans (FN-68) - #7839
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Cover the LoanPay side of the impairment fix from FN-9 (#6557): - with featureLendingProtocolV1_1, a plain LoanPay on an impaired, overdue loan is rejected with tecEXPIRED and only tfLoanLatePayment is accepted, clearing impairment with no residual vault LossUnrealized; - without the amendment, the original bypass reproduces (tesSUCCESS), proving the amendment is what closes it.
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High Level Overview of Change
Adds regression tests covering the LoanPay
side of the impairment fix in this branch (FN-9 / #6557). Stacked on
tapanito/lending-impairment; intended to land with that PR.Context of Change
FN-68 is a bug-bounty report: a borrower could bypass late-payment charges
by paying an impaired, overdue loan with a plain
LoanPay(notfLoanLatePayment). The pre-amendment auto-unimpair rewrotesfNextPaymentDueDateinto the future before the late check ran, so thepayment was accepted as on-time (
tesSUCCESS), skipping the late fee andlate interest — and the late path was itself unusable (
tecTOO_SOON).FN-9 already fixes the root cause under
featureLendingProtocolV1_1(impair/unimpair no longer move the due date; impairment is only allowed
once the payment is late). These tests assert that fix from the
borrower-facing LoanPay angle, which the existing FN-9 tests did not cover.
Changes
Two cases in
src/test/app/Loan_test.cpp:testImpairedOverdueLoanPayRequiresLateFlag(amendment enabled): on animpaired, overdue loan a plain
LoanPayreturnstecEXPIRED; the samepayment with
tfLoanLatePaymentsucceeds, clears impairment, advances theschedule, and leaves no residual
Vault.LossUnrealized.testImpairedOverdueLoanPayBypassPreAmendment(amendment disabled):reproduces the original bypass (
tesSUCCESS), proving the amendment iswhat closes it (guards against a vacuous test).
Type of Change