---
id: TST-PFM-ELG-476
title: Eligibility diff checks
kind: unit
product_area: platform
module: eligibility
revision: 1
status: draft
source_sha:
  services-platform: ad3f6a6582843008ed0f5a17b131878d15829af1
repository: services-platform
files:
  - modules/eligibility/tests/unit/diff.spec.js
implements: []
environment: mock
implementation_state: implemented
latest_result: not-run
conformance: not-verified
estimated_minutes: 1
isolation: One process with suite-local inputs.
evidence:
  - provenance: test
    source: 'services-platform:modules/eligibility/tests/unit/diff.spec.js'
    cases:
      - reports no change between a tree and itself
      - >-
        reports no change between two trees that differ only in the order their
        keys were written
      - >-
        names the value that changed and says it as the two readings of the
        condition
      - names the operator when the comparison changed
      - names the subject when the condition reads another slot
      - 'says a group changed its connective, without repeating its children'
      - reports only the kind when a node became another kind of node
      - says an added node as the condition it reads
      - says a removed node at its place in the earlier tree
      - 'matches a node by id wherever it moved, so a reordering is no change'
      - matches nodes without ids by their place in the tree
      - reports a subject slot the later tree declares and the earlier does not
      - names the property of a slot whose declaration changed
      - 'counts the additions, removals and changes it lists'
      - reports one change saying which version cannot be compared node by node
      - reports no change between two identical ungrammatical expressions
  - provenance: documented
    source: 'services-platform:modules/eligibility/tests/unit/diff.spec.js:suite header'
    note: >-
      The source header describes the verification boundary and declared
      substitutions.
proof_limit: >-
  No complete capability or feature scenario is mapped to this file; case-level
  ownership remains a coverage finding.
---

# Eligibility diff checks

## Verification Boundary

This suite checks isolated decisions and validation using the imported inputs. It cannot establish a complete service or browser lifecycle.

## What This Suite Proves

The file contains executable checks, but no complete scenario mapping is established here. Its source test titles identify the remaining mapping work.

## What It Does Not Prove

Registration supplies no execution result or conformance decision. Passing isolated checks does not establish deployed dependencies or cross-application delivery.

## Real Dependencies and Test Doubles

The suite runs isolated checks; its imported fixtures and injected collaborators define the substitutions. The source imports and suite header identify the exact dependencies.

## Must Not Be Doubled

The decision or validator being asserted remains real; returning the expected answer from a substitute defeats the check.