chore: import upstream snapshot with attribution

apps/sim/lib/table/events.test.ts

@@ -0,0 +1,78 @@
+/**
+ * @vitest-environment node
+ */
+import { beforeEach, describe, expect, it, vi } from 'vitest'
+
+vi.mock('@/lib/core/config/redis', () => ({
+  getRedisClient: () => null,
+}))
+
+vi.mock('@/lib/core/config/env', () => ({
+  env: { REDIS_URL: undefined },
+}))
+
+import type { TableEvent } from '@/lib/table/events'
+import { appendTableEvent, getLatestTableEventId, readTableEventsSince } from '@/lib/table/events'
+
+/** Module-level memory buffer can't be reset without vi.resetModules — use a
+ *  unique tableId per test to avoid cross-test bleed. */
+let seq = 0
+function uniqueTableId(): string {
+  seq++
+  return `table-events-test-${seq}`
+}
+
+function cellEvent(tableId: string): TableEvent {
+  return {
+    kind: 'cell',
+    tableId,
+    rowId: 'row-1',
+    groupId: 'group-1',
+    status: 'running',
+  }
+}
+
+describe('getLatestTableEventId (memory buffer)', () => {
+  beforeEach(() => {
+    vi.clearAllMocks()
+  })
+
+  it('returns 0 for a table with no events, without allocating a stream', async () => {
+    const tableId = uniqueTableId()
+    expect(await getLatestTableEventId(tableId)).toBe(0)
+    // A pure read must not have created a buffer: appending afterwards still
+    // starts the sequence at 1.
+    const entry = await appendTableEvent(cellEvent(tableId))
+    expect(entry?.eventId).toBe(1)
+  })
+
+  it('returns the latest assigned eventId after appends', async () => {
+    const tableId = uniqueTableId()
+    await appendTableEvent(cellEvent(tableId))
+    const second = await appendTableEvent(cellEvent(tableId))
+    expect(second?.eventId).toBe(2)
+    expect(await getLatestTableEventId(tableId)).toBe(2)
+  })
+
+  it('tailing from the latest id yields no replayed events', async () => {
+    const tableId = uniqueTableId()
+    await appendTableEvent(cellEvent(tableId))
+    await appendTableEvent(cellEvent(tableId))
+    const latest = await getLatestTableEventId(tableId)
+    const result = await readTableEventsSince(tableId, latest)
+    expect(result).toEqual({ status: 'ok', events: [] })
+  })
+
+  it('a subsequent append is visible to a reader tailing from the prior latest', async () => {
+    const tableId = uniqueTableId()
+    await appendTableEvent(cellEvent(tableId))
+    const latest = await getLatestTableEventId(tableId)
+    await appendTableEvent(cellEvent(tableId))
+    const result = await readTableEventsSince(tableId, latest)
+    expect(result.status).toBe('ok')
+    if (result.status === 'ok') {
+      expect(result.events).toHaveLength(1)
+      expect(result.events[0].eventId).toBe(latest + 1)
+    }
+  })
+})