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tests/unit/worker/user-concurrency-gate.test.ts

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+import { describe, expect, it } from 'vitest'
+import { withUserConcurrencyGate } from '@/lib/workers/user-concurrency-gate'
+
+function deferred<T>() {
+  let resolve!: (value: T | PromiseLike<T>) => void
+  const promise = new Promise<T>((nextResolve) => {
+    resolve = nextResolve
+  })
+  return { promise, resolve }
+}
+
+describe('user concurrency gate', () => {
+  it('serializes same-scope work for the same user when limit is 1', async () => {
+    const firstDone = deferred<void>()
+    const events: string[] = []
+
+    const first = withUserConcurrencyGate({
+      scope: 'image',
+      userId: 'user-1',
+      limit: 1,
+      run: async () => {
+        events.push('first:start')
+        await firstDone.promise
+        events.push('first:end')
+      },
+    })
+
+    const second = withUserConcurrencyGate({
+      scope: 'image',
+      userId: 'user-1',
+      limit: 1,
+      run: async () => {
+        events.push('second:start')
+        events.push('second:end')
+      },
+    })
+
+    await Promise.resolve()
+    expect(events).toEqual(['first:start'])
+
+    firstDone.resolve()
+    await Promise.all([first, second])
+
+    expect(events).toEqual([
+      'first:start',
+      'first:end',
+      'second:start',
+      'second:end',
+    ])
+  })
+})