Fix 2 flaky tests

[kvch]

Description

This PR fixes 2 flaky tests:

• pkg/wal/processor/transformer/wal_postgres_anon_rule_parser_test.go

Two subtests running in parallel registered a call to remove the same rules file. The error-marshaler case never creates a file, but its deferred cleanup still calls os.Remove. It can delete the success case's file before its os.Stat check runs.

• pkg/wal/processor/webhook/notifier/webhook_notifier_test.go

The test calls ProcessWALEvent in a default branch and asserts on the last processErr when doneChan fires. Now the notifier guarantees that any ProcessWALEvent called after Notify exits will see the closed notifyDone and return the wrapped error. So the fix is to make one more ProcessWALEvent call inside the doneChan case before asserting.

Type of Change

Please select the relevant option(s):

• 🐛 Bug fix (non-breaking change that fixes an issue)
• ✨ New feature (non-breaking change that adds functionality)
• 💥 Breaking change (fix or feature that would cause existing functionality to not work as expected)
• 📚 Documentation update
• 🔧 Refactoring (no functional changes)
• ⚡ Performance improvement
• 🧪 Test coverage improvement
• 🔨 Build/CI changes
• 🧹 Code cleanup

[github-actions]

Merging this branch will not change overall coverage

Impacted Packages	Coverage Δ	🤖
github.com/xataio/pgstream/pkg/wal/processor/transformer	84.90% (ø)
github.com/xataio/pgstream/pkg/wal/processor/webhook/notifier	86.61% (ø)

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Coverage by file

Changed unit test files

• github.com/xataio/pgstream/pkg/wal/processor/transformer/wal_postgres_anon_rule_parser_test.go
• github.com/xataio/pgstream/pkg/wal/processor/webhook/notifier/webhook_notifier_test.go