packager: add BatchProcessor-test

Reviewed By: davidaurelio

Differential Revision: D4468735

fbshipit-source-id: 8d20b44ef20aa24e72cd53182dbc34139a10df41

packages/metro-bundler/react-packager/src/lib/__tests__/BatchProcessor-test.js

@@ -0,0 +1,68 @@
+/**
+ * Copyright (c) 2016-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+'use strict';
+
+jest.dontMock('../BatchProcessor');
+
+const BatchProcessor = require('../BatchProcessor');
+
+describe('BatchProcessor', () => {
+
+  const options = {
+    maximumDelayMs: 500,
+    maximumItems: 3,
+    concurrency: 2,
+  };
+
+  it('aggregate items concurrently', () => {
+    const input = [...Array(9).keys()].slice(1);
+    const transform = e => e * 10;
+    const batches = [];
+    let concurrency = 0;
+    let maxConcurrency = 0;
+    const bp = new BatchProcessor(options, (items, callback) => {
+      ++concurrency;
+      expect(concurrency).toBeLessThanOrEqual(options.concurrency);
+      maxConcurrency = Math.max(maxConcurrency, concurrency);
+      batches.push(items);
+      setTimeout(() => {
+        callback(null, items.map(transform));
+        --concurrency;
+      }, 0);
+    });
+    const results = [];
+    const callback = (error, res) => {
+      expect(error).toBe(null);
+      results.push(res);
+    };
+    input.forEach(e => bp.queue(e, callback));
+    jest.runAllTimers();
+    expect(batches).toEqual([
+      [1, 2, 3],
+      [4, 5, 6],
+      [7, 8],
+    ]);
+    expect(maxConcurrency).toEqual(options.concurrency);
+    expect(results).toEqual(input.map(transform));
+  });
+
+  it('report errors', () => {
+    const error = new Error('oh noes');
+    const bp = new BatchProcessor(options, (items, callback) => {
+      process.nextTick(callback.bind(null, error));
+    });
+    let receivedError;
+    bp.queue('foo', err => { receivedError = err; });
+    jest.runAllTimers();
+    jest.runAllTicks();
+    expect(receivedError).toBe(error);
+  });
+
+});