Context: The port's graceful-failure contract was implicit in the way
each strategy returns None/[] on malformed input, but without tests it
was an accidental property that could regress silently. Codify it.
Two invariants, each backed by a fixture:
1. Junk email → empty list, never raise.
`unparseable.eml` is a pure-marketing IE newsletter with no order
data. All three strategies try and fail; parse_invest_engine_email
returns []. No exception leaks.
2. Partial HTML email → intact orders only.
`html_partial_match.eml` has two nested summary tables: one with a
valid VUAG order, one that is missing both the ticker and "Bought N
@ £P" rows (simulates IE dropping content mid-render). The parser
returns just the VUAG order.
No implementation change needed — the behaviour existed as a side
effect of _try_html_summary_table returning None on missing fields.
These tests lock it down so future refactors can't quietly break it.
Test plan:
poetry run pytest tests/providers/parsers/ -q → 8 passed in 0.19s
poetry run mypy broker_sync/providers/parsers/invest_engine.py tests/providers/parsers/test_invest_engine.py → clean
poetry run ruff check broker_sync/providers/parsers/invest_engine.py tests/providers/parsers/test_invest_engine.py → All checks passed!
poetry run yapf --diff → clean (no diff)
Manual verification:
- Load unparseable.eml → parse returns [].
- Load html_partial_match.eml → parse returns exactly 1 activity (VUAG).
87526898e6