Flush all watchers on empty queue

ts/test-both/util/waitBatcher_test.ts

@@ -0,0 +1,80 @@
+// Copyright 2021 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+
+import { assert } from 'chai';
+import * as sinon from 'sinon';
+
+import { createWaitBatcher } from '../../util/waitBatcher';
+
+describe('waitBatcher', () => {
+  it('should schedule a full batch', async () => {
+    const processBatch = sinon.fake.resolves(undefined);
+
+    const batcher = createWaitBatcher<number>({
+      name: 'test',
+      wait: 10,
+      maxSize: 2,
+      processBatch,
+    });
+
+    await Promise.all([batcher.add(1), batcher.add(2)]);
+
+    assert.ok(processBatch.calledOnceWith([1, 2]), 'Full batch on first call');
+  });
+
+  it('should schedule a partial batch', async () => {
+    const processBatch = sinon.fake.resolves(undefined);
+
+    const batcher = createWaitBatcher<number>({
+      name: 'test',
+      wait: 10,
+      maxSize: 2,
+      processBatch,
+    });
+
+    await batcher.add(1);
+
+    assert.ok(processBatch.calledOnceWith([1]), 'Partial batch on timeout');
+  });
+
+  it('should flush a partial batch', async () => {
+    const processBatch = sinon.fake.resolves(undefined);
+
+    const batcher = createWaitBatcher<number>({
+      name: 'test',
+      wait: 10000,
+      maxSize: 1000,
+      processBatch,
+    });
+
+    await Promise.all([batcher.add(1), batcher.flushAndWait()]);
+
+    assert.ok(
+      processBatch.calledOnceWith([1]),
+      'Partial batch on flushAndWait'
+    );
+  });
+
+  it('should flush a partial batch with new items added', async () => {
+    const processBatch = sinon.fake.resolves(undefined);
+
+    const batcher = createWaitBatcher<number>({
+      name: 'test',
+      wait: 10000,
+      maxSize: 1000,
+      processBatch,
+    });
+
+    await Promise.all([
+      (async () => {
+        await batcher.add(1);
+        await batcher.add(2);
+      })(),
+      batcher.flushAndWait(),
+    ]);
+
+    assert(processBatch.firstCall.calledWith([1]), 'First partial batch');
+    assert(processBatch.secondCall.calledWith([2]), 'Second partial batch');
+    assert(!processBatch.thirdCall);
+  });
+});