Parity harness

A few rectors change which Laravel rule object handles validation at runtime. The functional suite proves the source-to-source AST shape; the parity harness under tests/Parity/ proves the resulting rule sets produce equivalent error bags when Laravel runs them.

In scope, because semantics may change:

• SimplifyRuleWrappersRector promotes field()->rule('accepted') to typed chains.
• GroupWildcardRulesToEachRector folds wildcard siblings into each(...).
• PromoteFieldFactoryRector rewrites field()->required()->rule('string') to string()->required().

The pure-refactor rectors ship structural coverage only; their transformations do not change which rule class handles validation.

Writing a fixture

Each lives at tests/Parity/Fixture/<RectorName>/<case>.php and returns:

return [
    'rules_before' => ['field' => 'pre-rector-rule-shape'],
    'rules_after'  => ['field' => FluentRule::typed()->...],
    'payloads' => [
        'descriptive name' => ['field' => 'value-to-test'],
    ],
    // only when the divergence is intentional:
    'allowed_divergences' => [
        'descriptive name' => [
            'category'  => DivergenceCategory::ImplicitTypeConstraint,
            'rationale' => 'why this one is acceptable',
        ],
    ],
];

The harness validates each payload against both rule sets and diffs the error bags. Outcomes: MATCH, BEFORE_REJECTS_AFTER_PASSES, AFTER_REJECTS_BEFORE_PASSES, BOTH_REJECT_DIFFERENT_MESSAGES, BOTH_REJECT_DIFFERENT_ORDER, or SKIPPED for the database and closure denylist.

Allowed divergences

Some transformations legitimately change behaviour. boolean()->accepted() rejects the 'yes' and 'on' strings that bare accepted allows, because of boolean's implicit pre-check. Categorize with DivergenceCategory:

Category	Meaning
ImplicitTypeConstraint	the typed rule attaches a constraint the pre-rector form lacked
MessageKeyDrift	same outcome, different message-key path
AttributeLabelDrift	same outcome, :attribute renders differently
OrderDependentPipeline	same messages, different per-field order

The category constrains the allowed runtime outcome, so a mismatched one fails the test, and the rationale lives beside the divergence.

tests/Parity/CoverageTest.php asserts every in-scope rector has at least one fixture. A new semantics-changing rector has to extend that list and ship a fixture before it merges.