CI caught a real problem this introduced. `NotificationServiceTests`
already asserted the full-preview title and body, and both it and the new
redaction tests read `NotificationPrivacySettings` from
`UserDefaults.standard` in the same process. Whichever ran second
depended on the other's cleanup, so it passed locally and failed in CI:
XCTAssertEqual failed: ("🔒 new dm") is not equal to ("🔒 DM from Alice")
Fixed at the source rather than by ordering or serialization.
`NotificationService` now takes a `hidePreviewsProvider`, defaulting to
the real preference, so each test states which behavior it asserts. The
pre-existing test asks for previews shown and gains a redacted
counterpart; the redaction tests no longer touch the shared store.
`NotificationPrivacySettings` also gained store-injecting accessors so
the default-value and round-trip assertions can use an isolated suite
rather than mutating preferences other tests read.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
