Add notification epoch inline fallback test (#7162)

getEpochId() now computes a bounded epoch inline on cache miss (oldest
notification within the window) instead of returning 1, which would turn
every notification query into a full-table scan until the async pipeline
repopulates the cache. Adds coverage for the recent-id fallback and the
no-recent-notifications case. (Code change committed alongside the #7195
NotificationService edits.)

tests/Feature/Services/NotificationEpochFallbackTest.php

@@ -0,0 +1,62 @@
+<?php
+
+use App\Jobs\InternalPipeline\NotificationEpochUpdatePipeline;
+use App\Models\Notification;
+use App\Services\NotificationService;
+use Illuminate\Foundation\Testing\LazilyRefreshDatabase;
+use Illuminate\Support\Facades\Cache;
+use Illuminate\Support\Facades\Queue;
+
+uses(LazilyRefreshDatabase::class);
+
+/*
+|--------------------------------------------------------------------------
+| NotificationService epoch fallback
+|--------------------------------------------------------------------------
+|
+| When the cached epoch id is missing/expired, getEpochId() must return a
+| recent notification id (computed inline) so notification queries only scan
+| the last ~6 months. Returning 1 would force `WHERE id > 1`, scanning the
+| entire notifications table.
+|
+*/
+
+beforeEach(function () {
+    Queue::fake();
+    Cache::forget(NotificationService::EPOCH_CACHE_KEY.'6');
+});
+
+it('returns a recent notification id on cache miss instead of 1', function () {
+    $old = Notification::create([
+        'profile_id' => 1,
+        'actor_id' => 2,
+        'action' => 'like',
+        'created_at' => now()->subMonths(9),
+    ]);
+
+    $recent = Notification::create([
+        'profile_id' => 1,
+        'actor_id' => 2,
+        'action' => 'like',
+        'created_at' => now()->subMonth(),
+    ]);
+
+    $epoch = NotificationService::getEpochId();
+
+    expect($epoch)->toBe($recent->id);
+    expect($epoch)->not->toBe(1);
+    expect($epoch)->toBeGreaterThan($old->id);
+
+    Queue::assertPushed(NotificationEpochUpdatePipeline::class);
+});
+
+it('falls back to 1 when no recent notifications exist', function () {
+    Notification::create([
+        'profile_id' => 1,
+        'actor_id' => 2,
+        'action' => 'like',
+        'created_at' => now()->subYear(),
+    ]);
+
+    expect(NotificationService::getEpochId())->toBe(1);
+});