RN: add some test to module system

Reviewed By: davidaurelio

Differential Revision: D5862757

fbshipit-source-id: cf5c88c4bb9d65368df07f6e85b207c90565bad9

packages/metro-bundler/src/Resolver/polyfills/__tests__/require-test.js

@@ -0,0 +1,94 @@
+/**
+ * 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.
+ *
+ * @emails oncall+javascript_foundation
+ * @format
+ */
+
+'use strict';
+
+const babel = require('babel-core');
+const babelConfig = require('../../../babelRegisterOnly').config;
+const fs = require('fs');
+
+describe('require', () => {
+  const moduleSystemCode = (() => {
+    const {only, ...config} = babelConfig([]);
+    only;
+    const rawCode = fs.readFileSync(require.resolve('../require'), 'utf8');
+    return babel.transform(rawCode, config).code;
+  })();
+
+  // eslint-disable-next-line no-new-func
+  const createModuleSystem = new Function(
+    'global',
+    '__DEV__',
+    moduleSystemCode,
+  );
+
+  let moduleSystem;
+
+  beforeEach(() => {
+    moduleSystem = {};
+  });
+
+  it('works with plain bundles', () => {
+    createModuleSystem(moduleSystem, false);
+    expect(moduleSystem.require).not.toBeUndefined();
+    expect(moduleSystem.__d).not.toBeUndefined();
+
+    const mockExports = {foo: 'bar'};
+    const mockFactory = jest
+      .fn()
+      .mockImplementation(
+        (global, require, moduleObject, exports, dependencyMap) => {
+          moduleObject.exports = mockExports;
+        },
+      );
+
+    moduleSystem.__d(mockFactory, 1, [2, 3]);
+    expect(mockFactory).not.toBeCalled();
+
+    const m = moduleSystem.require(1);
+    expect(mockFactory.mock.calls.length).toBe(1);
+    expect(mockFactory.mock.calls[0][0]).toBe(moduleSystem);
+    expect(m).toBe(mockExports);
+    expect(mockFactory.mock.calls[0][4]).toEqual([2, 3]);
+  });
+
+  it('works with Random Access Modules (RAM) bundles', () => {
+    const mockExports = {foo: 'bar'};
+    const mockFactory = jest
+      .fn()
+      .mockImplementation(
+        (global, require, moduleObject, exports, dependencyMap) => {
+          moduleObject.exports = mockExports;
+        },
+      );
+
+    moduleSystem.nativeRequire = jest.fn().mockImplementation(moduleId => {
+      moduleSystem.__d(mockFactory, moduleId, [2, 3]);
+    });
+    createModuleSystem(moduleSystem, false);
+    expect(moduleSystem.require).not.toBeUndefined();
+    expect(moduleSystem.__d).not.toBeUndefined();
+
+    expect(moduleSystem.nativeRequire).not.toBeCalled();
+    expect(mockFactory).not.toBeCalled();
+
+    const m = moduleSystem.require(1);
+
+    expect(moduleSystem.nativeRequire.mock.calls.length).toBe(1);
+    expect(moduleSystem.nativeRequire).toBeCalledWith(1);
+
+    expect(mockFactory.mock.calls.length).toBe(1);
+    expect(mockFactory.mock.calls[0][0]).toBe(moduleSystem);
+    expect(m).toBe(mockExports);
+    expect(mockFactory.mock.calls[0][4]).toEqual([2, 3]);
+  });
+});