Files
workouts/WorkoutsTests/WriteBacklogTests.swift
rzen 6e440317c4 Restructure into a three-tab app with Progress, goals, and Meditation
The UX redesign's first landing (spec in UX-REDESIGN.md): ContentView
becomes a Today / Progress / Settings TabView, "Routine" replaces
"Split" in every user-facing string and view name (code-level types
keep their names), and workout starting moves to shared
WorkoutStarter / StartedWorkoutNavigator plumbing.

- New Progress tab: weekly goal streaks, workout trends, per-exercise
  weight progression, achievements, and the full history list
  (WorkoutLogsView -> WorkoutHistoryView).
- Goals: stable categories workouts roll up to, managed from Settings.
- New Meditation exercise + starter routine; timed sits record to
  Apple Health as Mind & Body sessions.

Claude-Session: https://claude.ai/code/session_012qw2itfzKyEJ1HpsFt8Ex4
2026-07-11 07:53:01 -04:00

475 lines
24 KiB
Swift

import Foundation
import SwiftData
import Testing
@testable import Workouts
/// Pins the pure decision table of `WriteBacklog` — the depth-1 per-document write
/// queue `SyncEngine` drains to disk. Every operation here is a `struct`-level
/// mutation with no I/O and no clock of its own, so replacement, retry bookkeeping,
/// backoff, and TTL pruning are all deterministic and directly testable.
/// `SyncEngineWriteQueueTests` below covers how the engine wires this into the cache
/// and the `save`/`delete`/`ingestFromWatch` call sites.
struct WriteBacklogTests {
private static let t0 = Date(timeIntervalSince1970: 1_700_000_000)
/// Mid-month, noon dates in the current time zone — matches
/// `WorkoutPathBucketingTests`'s pattern so a derived `relativePath` month bucket
/// can never be nudged across a boundary by a real-world UTC offset.
private func date(year: Int, month: Int, day: Int = 15, hour: Int = 12) -> Date {
var comps = DateComponents()
comps.year = year; comps.month = month; comps.day = day; comps.hour = hour
return Calendar(identifier: .gregorian).date(from: comps)!
}
private func workoutDoc(id: String, start: Date, updatedAt: Date, routineName: String? = nil) -> WorkoutDocument {
WorkoutDocument(
schemaVersion: WorkoutDocument.currentSchemaVersion, id: id, routineID: nil,
routineName: routineName, start: start, end: nil,
status: WorkoutStatus.notStarted.rawValue, createdAt: updatedAt, updatedAt: updatedAt,
logs: [], metrics: nil
)
}
/// Builds a `PendingWrite` with a workout payload and full control over every
/// bookkeeping field, so replacement/retry/backoff tests can set up exact
/// preconditions directly instead of driving them indirectly through `SyncEngine`.
private func pendingWorkout(
id: String, start: Date, timestamp: Date, enqueuedAt: Date, routineName: String? = nil,
attempts: Int = 0, lastAttemptAt: Date? = nil, faultMessage: String? = nil,
stalePaths: Set<String> = []
) -> PendingWrite {
PendingWrite(
payload: .workout(workoutDoc(id: id, start: start, updatedAt: timestamp, routineName: routineName)),
timestamp: timestamp, stalePaths: stalePaths, enqueuedAt: enqueuedAt,
attempts: attempts, lastAttemptAt: lastAttemptAt, faultMessage: faultMessage
)
}
// MARK: - enqueue
/// Enqueuing into an empty slot stores the write verbatim, and `count`/`isEmpty`
/// reflect the newly-occupied slot — the base case every replacement test below
/// builds on.
@Test func enqueueIntoEmptySlotStoresWrite() {
var backlog = WriteBacklog()
#expect(backlog.isEmpty)
#expect(backlog.count == 0)
let write = pendingWorkout(id: "01ENQUEUEEMPTY0000000001", start: Self.t0, timestamp: Self.t0, enqueuedAt: Self.t0)
backlog.enqueue(write)
#expect(!backlog.isEmpty)
#expect(backlog.count == 1)
#expect(backlog.pendingWrite(for: write.documentID)?.timestamp == Self.t0)
}
/// Newer-wins replacement: the incoming document's content takes the slot, but it
/// inherits the FIRST entry's retry bookkeeping (`enqueuedAt`, `attempts`,
/// `lastAttemptAt`, `faultMessage`) — resetting those on every edit would flap the
/// retry banner even though the backlog is failing for environmental reasons, not
/// because of what's in the slot. Stale paths union both sides' preexisting sets,
/// plus the occupant's now-abandoned target path (a month-rebucketing edit moves a
/// workout's file; an earlier attempt may already have landed at the old path).
@Test func newerWinsReplacementInheritsBookkeepingAndUnionsStalePaths() throws {
var backlog = WriteBacklog()
let id = "01NEWERWINS0000000000001"
let marchStart = date(year: 2024, month: 3)
let aprilStart = date(year: 2024, month: 4)
let oldTargetPath = "Workouts/2024/03/\(id).json"
let existing = pendingWorkout(
id: id, start: marchStart, timestamp: Self.t0,
enqueuedAt: Self.t0.addingTimeInterval(-100),
attempts: 2, lastAttemptAt: Self.t0.addingTimeInterval(-10), faultMessage: "disk full",
stalePaths: ["Workouts/2024/02/\(id).json"]
)
#expect(existing.targetPath == oldTargetPath)
backlog.enqueue(existing)
let incoming = pendingWorkout(
id: id, start: aprilStart, timestamp: Self.t0.addingTimeInterval(10),
enqueuedAt: Self.t0, // would be its own enqueuedAt if it were the first — must be overridden
stalePaths: ["Workouts/2024/05/\(id).json"]
)
backlog.enqueue(incoming)
let slot = try #require(backlog.pendingWrite(for: id))
#expect(slot.timestamp == incoming.timestamp)
guard case .workout(let doc) = slot.payload else {
Issue.record("expected a workout payload"); return
}
#expect(doc.start == aprilStart) // the newer document content wins the slot
#expect(slot.enqueuedAt == existing.enqueuedAt)
#expect(slot.attempts == existing.attempts)
#expect(slot.lastAttemptAt == existing.lastAttemptAt)
#expect(slot.faultMessage == existing.faultMessage)
#expect(slot.stalePaths.isSuperset(of: existing.stalePaths))
#expect(slot.stalePaths.isSuperset(of: incoming.stalePaths))
#expect(slot.stalePaths.contains(oldTargetPath))
}
/// An incoming write at exactly the occupant's timestamp still wins the slot —
/// equal timestamps are treated as the latest local re-save of the same logical
/// state, so last-in is correct.
@Test func equalTimestampIncomingWinsSlot() throws {
var backlog = WriteBacklog()
let id = "01EQUALTIMESTAMP000000001"
backlog.enqueue(pendingWorkout(id: id, start: Self.t0, timestamp: Self.t0, enqueuedAt: Self.t0, routineName: "Original"))
backlog.enqueue(pendingWorkout(id: id, start: Self.t0, timestamp: Self.t0, enqueuedAt: Self.t0, routineName: "Incoming"))
let slot = try #require(backlog.pendingWrite(for: id))
guard case .workout(let doc) = slot.payload else {
Issue.record("expected a workout payload"); return
}
#expect(doc.routineName == "Incoming")
}
/// An incoming write strictly older than the occupant is dropped outright — the
/// slot (and its bookkeeping) is left completely unchanged.
@Test func strictlyOlderIncomingIsDropped() throws {
var backlog = WriteBacklog()
let id = "01OLDERDROPPED0000000001"
backlog.enqueue(pendingWorkout(id: id, start: Self.t0, timestamp: Self.t0, enqueuedAt: Self.t0, routineName: "Kept"))
backlog.enqueue(pendingWorkout(id: id, start: Self.t0, timestamp: Self.t0.addingTimeInterval(-5), enqueuedAt: Self.t0, routineName: "Ignored"))
let slot = try #require(backlog.pendingWrite(for: id))
guard case .workout(let doc) = slot.payload else {
Issue.record("expected a workout payload"); return
}
#expect(doc.routineName == "Kept")
#expect(slot.timestamp == Self.t0)
}
// MARK: - resolve
/// `resolve(id:ifTimestampAtMost:)` is the replacement-safety property the drain
/// relies on: it removes the slot when the just-written version is still current
/// (`entry.timestamp <= given`), but a write that slotted in WHILE the attempt was
/// in flight (`entry.timestamp > given`) survives — the drain only just wrote the
/// OLD content, so the newer queued edit must not be discarded as if it had landed.
@Test func resolveRemovesOnlyWhenNoNewerWriteSlottedIn() throws {
var backlog = WriteBacklog()
let id = "01RESOLVESAFETY0000000001"
let firstAttemptTimestamp = Self.t0
backlog.enqueue(pendingWorkout(id: id, start: Self.t0, timestamp: firstAttemptTimestamp, enqueuedAt: Self.t0))
let newerTimestamp = Self.t0.addingTimeInterval(30)
backlog.enqueue(pendingWorkout(id: id, start: Self.t0, timestamp: newerTimestamp, enqueuedAt: Self.t0))
backlog.resolve(id: id, ifTimestampAtMost: firstAttemptTimestamp)
let survivor = try #require(backlog.pendingWrite(for: id))
#expect(survivor.timestamp == newerTimestamp)
backlog.resolve(id: id, ifTimestampAtMost: newerTimestamp)
#expect(backlog.pendingWrite(for: id) == nil)
}
// MARK: - markFailed
/// `markFailed` increments attempts and stamps `lastAttemptAt` on every call, only
/// overwrites `faultMessage` when a new one is supplied (an unrecoverable error
/// shouldn't be forgotten by a subsequent plain retry failure), `maxAttempts` is
/// the max across every slot, and `firstFaultMessage` walks slots oldest-`enqueuedAt`
/// first — so once the OLDEST slot also faults, its message takes priority even
/// though a newer slot faulted first in wall-clock time.
@Test func markFailedTracksAttemptsFaultPriorityAndMax() throws {
var backlog = WriteBacklog()
let older = "01MARKFAILEDOLDER00000001" // enqueued first
let newer = "01MARKFAILEDNEWER00000001" // enqueued second
backlog.enqueue(pendingWorkout(id: older, start: Self.t0, timestamp: Self.t0, enqueuedAt: Self.t0))
backlog.enqueue(pendingWorkout(id: newer, start: Self.t0, timestamp: Self.t0, enqueuedAt: Self.t0.addingTimeInterval(5)))
#expect(backlog.maxAttempts == 0)
#expect(backlog.firstFaultMessage == nil)
let failAt1 = Self.t0.addingTimeInterval(1)
backlog.markFailed(id: older, at: failAt1)
var entry = try #require(backlog.pendingWrite(for: older))
#expect(entry.attempts == 1)
#expect(entry.lastAttemptAt == failAt1)
#expect(entry.faultMessage == nil)
// `newer` is the only faulting slot so far — it surfaces even though `older`
// was enqueued earlier and hasn't faulted.
backlog.markFailed(id: newer, at: Self.t0.addingTimeInterval(2), fault: "disk full")
#expect(backlog.firstFaultMessage == "disk full")
// Once `older` (the earlier-enqueued slot) also faults, its message takes
// priority — `firstFaultMessage` walks entries oldest-first.
backlog.markFailed(id: older, at: Self.t0.addingTimeInterval(3), fault: "older fault")
#expect(backlog.firstFaultMessage == "older fault")
// A later failure with no new fault keeps the existing message rather than
// clearing it.
backlog.markFailed(id: older, at: Self.t0.addingTimeInterval(4))
entry = try #require(backlog.pendingWrite(for: older))
#expect(entry.attempts == 3)
#expect(entry.faultMessage == "older fault")
#expect(backlog.maxAttempts == 3) // older: 3 attempts, newer: 1
}
// MARK: - Backoff scheduling
/// `nextDue`/`earliestNextAttempt` are the drain loop's scheduling surface: a
/// fresh entry (never attempted) is due immediately at its `enqueuedAt`, and each
/// failure re-anchors the backoff at `retryDelay(afterAttempts:)` from the FAILURE
/// time — not cumulative, not from `enqueuedAt`.
@Test func nextDueAndEarliestNextAttemptHonorBackoff() throws {
var backlog = WriteBacklog()
let id = "01BACKOFFDUE0000000000001"
let enqueuedAt = Self.t0
backlog.enqueue(pendingWorkout(id: id, start: Self.t0, timestamp: Self.t0, enqueuedAt: enqueuedAt))
// A second, never-failing slot enqueued much later — present throughout so
// `earliestNextAttempt` is genuinely picking a minimum across slots, not just
// echoing the only one that exists.
let freshID = "01BACKOFFFRESH00000000001"
backlog.enqueue(pendingWorkout(id: freshID, start: Self.t0, timestamp: Self.t0, enqueuedAt: Self.t0.addingTimeInterval(10_000)))
var entry = try #require(backlog.pendingWrite(for: id))
#expect(entry.nextAttemptAt == enqueuedAt)
#expect(backlog.nextDue(at: enqueuedAt.addingTimeInterval(-1)) == nil)
#expect(backlog.nextDue(at: enqueuedAt)?.documentID == id)
#expect(backlog.earliestNextAttempt() == enqueuedAt)
let firstFailure = Self.t0.addingTimeInterval(100)
backlog.markFailed(id: id, at: firstFailure)
entry = try #require(backlog.pendingWrite(for: id))
let expectedFirstRetry = firstFailure.addingTimeInterval(WriteBacklog.retryDelay(afterAttempts: 1))
#expect(entry.nextAttemptAt == expectedFirstRetry)
#expect(backlog.nextDue(at: expectedFirstRetry.addingTimeInterval(-0.5)) == nil)
#expect(backlog.nextDue(at: expectedFirstRetry)?.documentID == id)
let secondFailure = expectedFirstRetry.addingTimeInterval(50)
backlog.markFailed(id: id, at: secondFailure)
entry = try #require(backlog.pendingWrite(for: id))
let expectedSecondRetry = secondFailure.addingTimeInterval(WriteBacklog.retryDelay(afterAttempts: 2))
#expect(entry.nextAttemptAt == expectedSecondRetry)
#expect(backlog.earliestNextAttempt() == expectedSecondRetry)
}
/// Locks the exact backoff table: three quick silent retries (2s/4s/8s), then calm
/// long retries, capped at 5 minutes from attempt 7 onward.
@Test func retryDelayScheduleMatchesBackoffTable() {
#expect(WriteBacklog.retryDelay(afterAttempts: 0) == 0)
#expect(WriteBacklog.retryDelay(afterAttempts: 1) == 2)
#expect(WriteBacklog.retryDelay(afterAttempts: 2) == 4)
#expect(WriteBacklog.retryDelay(afterAttempts: 3) == 8)
#expect(WriteBacklog.retryDelay(afterAttempts: 4) == 30)
#expect(WriteBacklog.retryDelay(afterAttempts: 5) == 60)
#expect(WriteBacklog.retryDelay(afterAttempts: 6) == 120)
#expect(WriteBacklog.retryDelay(afterAttempts: 7) == 300)
#expect(WriteBacklog.retryDelay(afterAttempts: 50) == 300) // capped, not just "7"
}
// MARK: - pruneExpired
/// A persisted backlog loaded on relaunch drops any slot stuck longer than the
/// TTL — a run that died with a queued write shouldn't drain stale state into a
/// container that's long since moved on — while a younger slot survives untouched.
@Test func pruneExpiredDropsOnlyEntriesPastTheTTL() throws {
var backlog = WriteBacklog()
let now = Self.t0
let ttl: TimeInterval = 60
let youngID = "01PRUNEYOUNG0000000000001"
let oldID = "01PRUNEOLD0000000000000001"
backlog.enqueue(pendingWorkout(id: youngID, start: Self.t0, timestamp: Self.t0, enqueuedAt: now.addingTimeInterval(-30)))
backlog.enqueue(pendingWorkout(id: oldID, start: Self.t0, timestamp: Self.t0, enqueuedAt: now.addingTimeInterval(-90)))
backlog.pruneExpired(now: now, ttl: ttl)
#expect(backlog.pendingWrite(for: youngID) != nil)
#expect(backlog.pendingWrite(for: oldID) == nil)
#expect(backlog.count == 1)
}
// MARK: - WriteBacklogFile
/// The sidecar file round-trips a non-empty backlog's slots (ids and timestamps
/// intact), and saving an EMPTY backlog removes any existing file instead of
/// writing `{}` — the sidecar's absence IS "no pending writes," matching what a
/// fresh install/relaunch with nothing queued looks like on disk.
@Test func fileRoundTripPreservesSlotsAndEmptySaveRemovesFile() throws {
let url = FileManager.default.temporaryDirectory.appending(path: UUID().uuidString + ".json")
defer { try? FileManager.default.removeItem(at: url) }
var backlog = WriteBacklog()
let idA = "01FILEROUNDTRIPA00000001"
let idB = "01FILEROUNDTRIPB00000001"
backlog.enqueue(pendingWorkout(id: idA, start: Self.t0, timestamp: Self.t0, enqueuedAt: Self.t0))
backlog.enqueue(pendingWorkout(id: idB, start: Self.t0, timestamp: Self.t0.addingTimeInterval(5), enqueuedAt: Self.t0.addingTimeInterval(5)))
WriteBacklogFile.save(backlog, to: url)
#expect(FileManager.default.fileExists(atPath: url.path))
let loaded = WriteBacklogFile.load(from: url)
#expect(loaded.count == 2)
#expect(loaded.pendingWrite(for: idA)?.timestamp == Self.t0)
#expect(loaded.pendingWrite(for: idA)?.documentID == idA)
#expect(loaded.pendingWrite(for: idB)?.timestamp == Self.t0.addingTimeInterval(5))
// Saving an EMPTY backlog over an existing file removes it rather than
// writing `{}`.
WriteBacklogFile.save(WriteBacklog(), to: url)
#expect(!FileManager.default.fileExists(atPath: url.path))
}
}
// MARK: - SyncEngine integration
/// Coverage for `SyncEngine`'s write-queue integration: every `save`/`delete` mirrors
/// into the SwiftData cache immediately and enqueues the file write (see
/// `WriteBacklogTests` above for the queue's own pure mechanics). None of these tests
/// call `connect()` — matching `SyncEngineTests`'s scope note, the engine's `store`
/// stays nil, so `kickDrain()` never launches a background drain that could race these
/// assertions, and no real iCloud container is ever touched. Each test builds its own
/// `SyncEngine` against a fresh in-memory `ModelContainer` and a unique temp
/// `backlogURL`, so tests can't contaminate each other or the developer's real
/// Application Support directory.
struct SyncEngineWriteQueueTests {
private static let t0 = Date(timeIntervalSince1970: 1_700_000_000)
private func tempBacklogURL() -> URL {
FileManager.default.temporaryDirectory.appending(path: "WriteBacklogTests-\(UUID().uuidString).json")
}
@MainActor
private func makeEngine(backlogURL: URL) throws -> (engine: SyncEngine, container: ModelContainer) {
let schema = Schema([Routine.self, Exercise.self, Workout.self, WorkoutLog.self])
let config = ModelConfiguration(schema: schema, isStoredInMemoryOnly: true, cloudKitDatabase: .none)
let container = try ModelContainer(for: schema, configurations: [config])
return (SyncEngine(container: container, backlogURL: backlogURL), container)
}
private func makeWorkoutDoc(id: String, updatedAt: Date, routineName: String? = "Push Day") -> WorkoutDocument {
WorkoutDocument(
schemaVersion: WorkoutDocument.currentSchemaVersion, id: id, routineID: "RT-1",
routineName: routineName, start: Self.t0, end: nil,
status: WorkoutStatus.notStarted.rawValue, createdAt: Self.t0, updatedAt: updatedAt,
logs: [], metrics: nil
)
}
// MARK: - save(workout:)
/// A local save mirrors into the cache immediately (a same-process write doesn't
/// reliably wake the metadata observer, and never does in the simulator) and
/// queues exactly one write.
@MainActor
@Test func saveWorkoutMirrorsToCacheAndQueuesWrite() async throws {
let (engine, container) = try makeEngine(backlogURL: tempBacklogURL())
let id = "01SAVEQUEUE0000000000001"
await engine.save(workout: makeWorkoutDoc(id: id, updatedAt: Self.t0))
let cached = try #require(CacheMapper.fetchWorkout(id: id, in: container.mainContext))
#expect(cached.updatedAt == Self.t0)
#expect(engine.pendingWriteCount == 1)
#expect(engine.writeQueueState == .pending)
}
/// Depth-1 per-document slot: saving the same id twice keeps exactly one queued
/// write, and the cache — which every save mirrors into unconditionally — shows
/// the LATEST version, matching what the eventually-drained file will contain.
@MainActor
@Test func repeatedSaveSameIDStaysDepthOneWithNewestCached() async throws {
let (engine, container) = try makeEngine(backlogURL: tempBacklogURL())
let id = "01DEPTHONE00000000000001"
await engine.save(workout: makeWorkoutDoc(id: id, updatedAt: Self.t0))
await engine.save(workout: makeWorkoutDoc(id: id, updatedAt: Self.t0.addingTimeInterval(60)))
#expect(engine.pendingWriteCount == 1)
let cached = try #require(CacheMapper.fetchWorkout(id: id, in: container.mainContext))
#expect(cached.updatedAt == Self.t0.addingTimeInterval(60))
}
// MARK: - ingestFromWatch
/// The watch bridge's `updatedAt` intake gate: a strictly-older push is dropped
/// (the cache is already ahead of the watch), an equal timestamp is the
/// echo/duplicate case and is ignored wholesale even when some other field
/// differs, and a strictly-newer push is accepted. `sendMessage` plus a queued
/// `transferUserInfo` fallback are unordered, so this gate is what keeps a stale
/// racing push from clobbering a newer local save.
@MainActor
@Test func ingestFromWatchAppliesUpdatedAtGate() async throws {
let (engine, container) = try makeEngine(backlogURL: tempBacklogURL())
let id = "01INGESTGATE000000000001"
await engine.save(workout: makeWorkoutDoc(id: id, updatedAt: Self.t0, routineName: "Push Day"))
// (a) strictly older — dropped, cache unchanged.
await engine.ingestFromWatch(makeWorkoutDoc(id: id, updatedAt: Self.t0.addingTimeInterval(-60), routineName: "Push Day"))
var cached = try #require(CacheMapper.fetchWorkout(id: id, in: container.mainContext))
#expect(cached.updatedAt == Self.t0)
// (b) same updatedAt but a changed field — the echo case, ignored entirely
// (equal timestamp means duplicate, not a genuine edit).
await engine.ingestFromWatch(makeWorkoutDoc(id: id, updatedAt: Self.t0, routineName: "Changed Name"))
cached = try #require(CacheMapper.fetchWorkout(id: id, in: container.mainContext))
#expect(cached.updatedAt == Self.t0)
#expect(cached.routineName == "Push Day")
// (c) strictly newer — accepted.
await engine.ingestFromWatch(makeWorkoutDoc(id: id, updatedAt: Self.t0.addingTimeInterval(60), routineName: "Changed Name"))
cached = try #require(CacheMapper.fetchWorkout(id: id, in: container.mainContext))
#expect(cached.updatedAt == Self.t0.addingTimeInterval(60))
#expect(cached.routineName == "Changed Name")
}
/// A queued-but-unwritten delete vetoes resurrection: a watch push racing the
/// delete — even carrying an `updatedAt` newer than the deleted version — must
/// not bring the entity back, because the delete's stub simply hasn't landed on
/// disk yet (the same veto an already-written tombstone would apply).
@MainActor
@Test func pendingDeleteVetoesWatchIngestResurrection() async throws {
let (engine, container) = try makeEngine(backlogURL: tempBacklogURL())
let id = "01DELETEVETO0000000000001"
await engine.save(workout: makeWorkoutDoc(id: id, updatedAt: Self.t0))
let entity = try #require(CacheMapper.fetchWorkout(id: id, in: container.mainContext))
await engine.delete(workout: entity)
await engine.ingestFromWatch(makeWorkoutDoc(id: id, updatedAt: Self.t0.addingTimeInterval(120)))
#expect(CacheMapper.fetchWorkout(id: id, in: container.mainContext) == nil)
}
// MARK: - Restore lifecycle
/// `beginRestore()` clears the backlog outright — queued writes reference
/// pre-restore state, and draining them into the just-restored tree would
/// reintroduce edits the user chose to roll back by restoring a backup.
@MainActor
@Test func beginRestoreClearsBacklogAndResetsQueueState() async throws {
let (engine, _) = try makeEngine(backlogURL: tempBacklogURL())
await engine.save(workout: makeWorkoutDoc(id: "01RESTORECLEAR00000001", updatedAt: Self.t0))
#expect(engine.pendingWriteCount == 1)
engine.beginRestore()
#expect(engine.pendingWriteCount == 0)
#expect(engine.writeQueueState == .idle)
engine.endRestore() // balance the begin/end pair, matching every production call site
}
// MARK: - Persistence
/// The backlog sidecar survives across process launches: a second engine pointed
/// at the SAME `backlogURL` picks up the first engine's still-queued write on
/// `init`, before ever connecting — this is what lets a killed app resume
/// draining on next launch instead of silently losing the edit.
@MainActor
@Test func backlogPersistsAcrossEngineInstancesSharingBacklogURL() async throws {
let url = tempBacklogURL()
defer { try? FileManager.default.removeItem(at: url) }
let (engineA, _) = try makeEngine(backlogURL: url)
await engineA.save(workout: makeWorkoutDoc(id: "01PERSISTBACKLOG000001", updatedAt: Self.t0))
#expect(engineA.pendingWriteCount == 1)
let (engineB, _) = try makeEngine(backlogURL: url)
#expect(engineB.pendingWriteCount == 1)
}
}