docs: Expand testing guidelines for exception groups and context managers

- Updated `AGENTS.md` and `TESTING_GUIDELINES.md` with instructions on
  handling `ExceptionGroup` subclasses like `PdfRestErrorGroup` in tests.
- Emphasized verifying individual errors within `ExceptionGroups` using
  `pytest.RaisesGroup` and the `check=` hook for improved test accuracy.
- Added guidance to use a single `with` statement for combined context
  managers in compliance with ruff's SIM117 rule.

Assisted-by: Codex

Author: datalogics-kam

AGENTS.md

@@ -138,11 +138,21 @@
 - Write pytest tests: files named `test_*.py`, test functions `test_*`, fixtures
   in `conftest.py` where shared.
 
+- Follow ruff’s SIM117 rule: when combining context managers (e.g., a client and
+  `pytest.RaisesGroup`), use a single `with (...)` statement instead of nesting
+  them to keep tests idiomatic and lint-clean.
+
 - Cover both client transports in every new test module (unit and live suites):
   add distinct test cases (not parameterized branches) that exercise each
   assertion through `PdfRestClient` and `AsyncPdfRestClient` so sync/async
   behaviour stays independently verifiable.
 
+- When endpoints may raise `PdfRestErrorGroup` (or any future pdfRest-specific
+  exception groups), assert them with `pytest.RaisesGroup`/`pytest.RaisesExc`,
+  and use the `check=` hook to confirm the outer group is the expected class so
+  each inner error is validated individually rather than matching the group
+  message alone.
+
 - Ensure high-value coverage of public functions and edge cases; document intent
   in test docstrings when non-obvious.
 

TESTING_GUIDELINES.md

@@ -222,10 +222,16 @@ iteration required.
   - Local validation failures (`ValidationError`, `ValueError`) that should
     prevent HTTP calls.
   - Server/transport failures (`PdfRestApiError`, `PdfRestAuthenticationError`,
-    `PdfRestTimeoutError`, `PdfRestTransportError`).
+    `PdfRestTimeoutError`, `PdfRestTransportError`, `PdfRestErrorGroup`, etc.).
 - When behaviour should short-circuit locally (bad UUIDs, empty query lists,
   missing profiles), configure the transport to raise if invoked so the test
   proves no HTTP request occurs.
+- When endpoints intentionally raise pdfRest-specific `ExceptionGroup`
+  subclasses (such as `PdfRestErrorGroup` produced by delete failures), capture
+  them with `pytest.RaisesGroup`/`pytest.RaisesExc`, and use the `check=` hook
+  to assert the aggregate is the expected group class. This verifies both the
+  group message and each individual member (`PdfRestDeleteError`, future custom
+  errors) instead of relying on the aggregate text alone.
 
 ## Additional Expectations