---
id: TST-ACC-BKS-172
title: Exchange Rate Rules rule suite
kind: unit
product_area: accounting
module: books
revision: 1
status: draft
source_sha:
  services-accounting: f47cb263875bbc0c5640fba7dae6785ec32695f8
  react-console: baf6dae382d6f41dce976c7f848667ccc37e076f
repository: services-accounting
files:
  - modules/books/tests/unit/rules/exchange-rate-rules.spec.js
implements:
  - ATS-ACC-BKS-004-01
  - ATS-ACC-BKS-004-06
environment: mock
implementation_state: implemented
latest_result: not-run
latest_run_at: null
latest_run_ref: null
conformance: not-verified
estimated_minutes: 1
isolation: Each example owns its input values and configured doubles.
assertion_bindings:
  - scenario: ATS-ACC-BKS-004-01
    source: >-
      services-accounting:modules/books/tests/unit/rules/exchange-rate-rules.spec.js#refuses
      a number (digits would be lost), zero, a negative, more than ten places,
      nine integer digits and a word
  - scenario: ATS-ACC-BKS-004-06
    source: >-
      services-accounting:modules/books/tests/unit/rules/exchange-rate-rules.spec.js#applies
      the target currency’s exponent exactly: 100.00 USD at 149.37 is 14937 yen
  - scenario: ATS-ACC-BKS-004-06
    source: >-
      services-accounting:modules/books/tests/unit/rules/exchange-rate-rules.spec.js#rounds
      half away from zero, for a credit too
  - scenario: ATS-ACC-BKS-004-06
    source: >-
      services-accounting:modules/books/tests/unit/rules/exchange-rate-rules.spec.js#converts
      the other way, rounded half up to ten places
unmapped: false
evidence:
  - provenance: test
    source: >-
      services-accounting:modules/books/tests/unit/rules/exchange-rate-rules.spec.js
execution_notes: >-
  The file exists at the pinned revision; this registration records no execution
  result.
---

# Exchange Rate Rules rule suite

## Verification Boundary

The suite evaluates books configuration logic directly. Its boundary is the called functions and configured dependencies, rather than a running service.

## What This Suite Proves

The individual assertion references identify the acceptance outcomes this file exercises. When a scenario spans several suites, this file supplies only its listed assertions; qualification must include the other bindings and any recorded coverage finding.

## What It Does Not Prove

Direct function checks do not prove route enforcement, transaction behavior or deployed integration. No result is claimed for the pinned revision until the suite runs and its evidence is reviewed.

## Real Dependencies and Test Doubles

The called rule or mapping functions are real code. Test inputs and any dependency doubles remain confined to individual examples.

## Must Not Be Doubled

The production function or carried adapter named by the file remains the subject under test; a second implementation of its expected answer is not a substitute.