m12-pr17: action-gate contract pin (tests/ai/test_action_gate.py)

[BalaShankar9]

m12-pr17: action-gate contract pin (tests/ai/test_action_gate.py)

Adds 21 tests pinning cross-cutting invariants of the "action gate"
(Dispatcher.invoke per blueprint section 6.2 — the single chokepoint
that decides whether a model-proposed tool call may execute).

Existing tests in ai_engine/tests/registry/test_dispatcher.py already
cover mechanism (grant flow, capability tokens, sandbox routing, schema
validation). This file pins the cross-cutting CONTRACTS that hold
across every code path — the boundary itself.

Invariants pinned (8 groups, 21 tests)

1. Status enum is closed: every emitted status in
   {ok, denied, invalid_input, invalid_output, timeout, error}.
   Drives every branch in one test, asserts no surprise statuses leak.
2. Audit row count = 1 per invoke (parametrized across all 6 branches).
   Catches double-write or silent-skip regressions.
3. Resolver never called on a deny (grant deny, invalid input,
   capability missing, unknown tool). Side-effect-freedom on the
   deny path is the whole point of the gate.
4. duration_ms >= 0 on every audit row (no monotonic-clock skew).
5. error_message truncated to 500 chars (DB column cap).
6. input_hash deterministic across identical args, distinct for
   different args, order-independent (json sort_keys contract).
7. org_id / user_id propagate to audit row across ok/denied/
   invalid_input/error branches.
8. Sink failure never masks tool result OR original tool exception
   type — operators rely on exception type for incident response.

Why "action gate" vs "dispatcher": semantic. The blueprint calls this
the action gate; the file is named after the boundary, not the class.
Anyone searching for "where do we enforce that a model cannot directly
take an action" will find this file first.

Files

• backend/tests/ai/init.py (new, empty)
• backend/tests/ai/test_action_gate.py (new, 21 tests)
• context/TESTING_CONTEXT.md (Shipped m12-pr17 section)
• context/CHANGELOG_INTELLIGENCE.md (m12-pr17 row)

Validation

• pytest tests/ai/test_action_gate.py -v -> 21 passed in 0.16s
• No other tests touched; no production code touched.

Stacked on PR #34 (m12-pr16). Base branch: m12-pr16-test-partition-health.

[Copilot]

Pull request overview

Adds a new contract-style test suite that pins cross-cutting invariants of the “action gate” (ai_engine.registry.Dispatcher.invoke) and updates the project’s testing/changelog context docs to reflect the shipped work.

Changes:

• Introduces backend/tests/ai/test_action_gate.py with 21 tests covering status closure, audit row guarantees, deny-path side-effect freedom, hashing determinism, propagation of org/user IDs, and sink best-effort behavior.
• Adds backend/tests/ai/__init__.py to formalize the test package.
• Updates /context documentation (TESTING_CONTEXT.md, CHANGELOG_INTELLIGENCE.md) to record m12-pr17 as shipped.

Reviewed changes

Copilot reviewed 3 out of 4 changed files in this pull request and generated 2 comments.

File	Description
context/TESTING_CONTEXT.md	Documents the new “action gate” contract test coverage under Shipped (m12-pr17).
context/CHANGELOG_INTELLIGENCE.md	Adds the m12-pr17 ledger entry and links m12-pr16 to PR #34.
backend/tests/ai/init.py	Adds an empty package marker for backend.tests.ai.
backend/tests/ai/test_action_gate.py	New contract test suite pinning Dispatcher.invoke invariants across success/deny/error branches.

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