---
id: TST-COM-ORD-130
title: 'Billing arithmetic: purity'
kind: unit
product_area: commerce
module: orders
revision: 1
status: draft
source_sha:
  services-commerce: c8b66a98e2490617aec38ba5c8165dd9bd0a8f9b
repository: services-commerce
files:
  - modules/orders/tests/unit/billing/purity.spec.js
implements: []
environment: mock
implementation_state: implemented
latest_result: not-run
latest_run_at: null
latest_run_ref: null
conformance: not-verified
estimated_minutes: 1
isolation: 'The suite owns its in-memory inputs, scripted responses and rendered component state.'
evidence:
  - provenance: test
    source: 'services-commerce:modules/orders/tests/unit/billing/purity.spec.js'
    test_cases:
      - finds the directory’s files (premise)
      - refuses a sample import of every forbidden kind (the guard bites)
      - 'imports no table, no persistence and nothing that reads, in any pure file'
scenario_coverage: []
dependency_evidence:
  provenance: test
  source: 'services-commerce:modules/orders/tests/unit/billing/purity.spec.js'
  declared_by_test: 'the directory''s files. Doubled: nothing.'
---

# Billing arithmetic: purity

## Verification Boundary

The unit suite checks the named contract or helper with controlled inputs.

## What This Suite Proves

The registered cases check billing arithmetic: purity with their fixture records and assertions. Scenario bindings name only the examples those cases exercise.

## What It Does Not Prove

A registered file supplies no run result or verified conformance by itself. Local fixtures do not establish deployed cross-service behavior or complete browser journeys.

## Real Dependencies and Test Doubles

Inputs and external responses are controlled in process; this suite establishes no deployed service behavior.

## Must Not Be Doubled

The named contract validation or component behavior under assertion must use its actual implementation.