test: added test for ConcurrentQueue

src/util/__tests__/ConcurrentQueue.test.ts

@@ -0,0 +1,108 @@
+import { ConcurrentQueue } from '../ConcurrentQueue';
+
+class SimpleQueue<T, R = void> extends ConcurrentQueue<T> {
+  handler(_item: T): Promise<R> {
+    throw new Error('Method not overriden');
+  }
+}
+
+test('should be able to process the queue within limit', async () => {
+  const inputs: number[] = [];
+  const queuedResolver: (() => void)[] = [];
+  const queue = new SimpleQueue<number>(3);
+
+  try {
+    vi.spyOn(queue, 'handler').mockImplementation((item) => {
+      inputs.push(item);
+      return new Promise((resolve, _reject) => {
+        queuedResolver.push(resolve);
+      });
+    });
+
+    const promises = [
+      // Add some values
+      queue.add(1),
+      queue.add(2),
+      queue.add(3),
+      queue.add(4),
+      queue.add(5),
+    ];
+
+    // Should queue 3 things at once
+    expect(queue.handler).toHaveBeenCalledTimes(3);
+    expect(inputs).toEqual([1, 2, 3]);
+
+    // Let first 3 go
+    for (let i = 0; i < 3; i++) {
+      queuedResolver[i]();
+      await promises[i];
+    }
+
+    // Wait till all fullfilled
+    while (queuedResolver.length !== 5) {
+      await new Promise((resolve) => setImmediate(resolve));
+    }
+
+    // Now it should've queued everything.
+    expect(inputs).toEqual([1, 2, 3, 4, 5]);
+    expect(queue.handler).toHaveBeenCalledTimes(5);
+
+    // Resolve everything
+    queuedResolver.forEach((resolve) => resolve());
+    await Promise.all(promises);
+  } finally {
+    vi.spyOn(queue, 'handler').mockRejectedValue(new Error('handler ran too late'));
+    queuedResolver.forEach((resolve) => resolve());
+  }
+});
+
+test('it should move on to the next item in the queue once failed', async () => {
+  const inputs: number[] = [];
+  const queuedResolver: (() => void)[] = [];
+  const queue = new SimpleQueue<number, number>(3);
+
+  try {
+    vi.spyOn(queue, 'handler').mockImplementation((item) => {
+      if (item === 3) {
+        throw new Error('dummy error');
+      }
+
+      inputs.push(item);
+      return new Promise((resolve, _reject) => {
+        queuedResolver.push(() => resolve(item));
+      });
+    });
+
+    const promises = [
+      // Add some values
+      queue.add(1),
+      queue.add(2),
+    ];
+    const errorHandler = vi.fn();
+    const badPromise = queue.add(3);
+    badPromise.catch(errorHandler);
+    promises.push(queue.add(4));
+    promises.push(queue.add(5));
+
+    // Let first 2 be fullfilled
+    for (let i = 0; i < 2; i++) {
+      queuedResolver[i]();
+      await promises[i];
+    }
+
+    // Wait till all fullfilled
+    while (queuedResolver.length !== 4) {
+      await new Promise((resolve) => setImmediate(resolve));
+    }
+
+    // Should've moved on, as 3 will throw error
+    expect(queue.handler).toHaveBeenCalledTimes(5);
+    await expect(badPromise).rejects.toThrowError('dummy error');
+
+    queuedResolver.forEach((resolve) => resolve());
+    expect(Promise.all(promises)).resolves.toEqual([1, 2, 4, 5]);
+  } finally {
+    vi.spyOn(queue, 'handler').mockRejectedValue(new Error('handler ran too late'));
+    queuedResolver.forEach((resolve) => resolve());
+  }
+});