Both helpers were exercised indirectly through MatchOriginalWrite /
MatchPath; pinning them directly catches a regression at the helper
level so a Match-test failure isn't the first signal of a broken
filter.
prefixMatches: empty prefix fast path; exact-prefix match; non-match
rejection; path shorter than prefix.
filterAllows: no-filter accepts any event; FilterSizeGreaterThan is
strictly > (boundary value rejected); FilterSizeLessThan is strictly
<; zero-size thresholds mean "not set" (must let any size through —
a regression treating 0 as a real threshold would reject everything);
required tag present accepts; missing key, empty tags map, wrong
value, and missing-among-multiple all reject; size + tag filters are
AND'd so either failing rejects.
