Templating Test Coverage Design

Context

apps/notify/templating.py is at 64% coverage. The existing tests thoroughly cover the Jinja2 template files (email, slack, pagerduty, generic, incident) but barely test the Python templating engine and service code itself.

Changes

1. Add tests for render_template function

Cover: None/empty spec, dict specs (inline/file), auto-detect file from string, unsupported spec type raises ValueError, file not found raises ValueError, _SafeDict missing key fallback, Jinja2 render error propagation.

2. Add tests for NotificationTemplatingService

compose_incident_details: psutil fallbacks (mocked), psutil exception handling, recommendation normalization (dict-of-dicts → list, single dict → list, scalar → list), _gb() with None, recs_pretty formatting.

render_message_templates: config key resolution (template/text_template/payload_template), default file candidate fallback chain, no template found raises ValueError, HTML template from config, HTML fallback to driver_html.j2, missing HTML → None.

3. Mock psutil

All compose_incident_details tests mock psutil so they’re deterministic and CI-portable.

Target

100% branch coverage on apps/notify/templating.py.