Added module mock example

examples/module_mock/.babelrc

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+{
+  "presets": ["env"]
+}

examples/module_mock/__tests__/full_mock.js

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+// Copyright 2004-present Facebook. All Rights Reserved.
+
+import DefaultExport, {apple, strawberry} from '../fruit';
+
+/**
+ * This file illustrates a full mock of a module.
+ */
+jest.mock('../fruit');
+
+describe('test', () => {
+  it('calls', () => {
+    expect(DefaultExport()).toBe(undefined);
+    expect(apple).toBe('apple');
+    expect(strawberry()).toBe(undefined);
+  });
+});

examples/module_mock/__tests__/partial_mock.js

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+// Copyright 2004-present Facebook. All Rights Reserved.
+
+/**
+ * This file illustrates how to do a partial mock where a subset
+ * of a module's exports have been mocked and the rest
+ * keep their actual implementation.
+ */
+import DefaultExport, {apple, strawberry} from '../fruit';
+
+jest.mock('../fruit', () => {
+  const originalModule = require.requireActual('../fruit');
+  const mockedModule = jest.genMockFromModule('../fruit');
+
+  //Mock the default export and named export 'apple'.
+  return Object.assign({}, mockedModule, originalModule, {
+    apple: 'mocked apple',
+    default: jest.fn(() => 'mocked fruit'),
+  });
+});
+
+describe('test', () => {
+  it('calls', () => {
+    const defaultExportResult = DefaultExport();
+    expect(defaultExportResult).toBe('mocked fruit');
+    expect(DefaultExport).toHaveBeenCalled();
+
+    expect(apple).toBe('mocked apple');
+    expect(strawberry()).toBe('strawberry');
+  });
+});

examples/module_mock/fruit.js

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+// Copyright 2004-present Facebook. All Rights Reserved.
+
+export const apple = 'apple';
+
+export const strawberry = () => 'strawberry';
+
+export default () => 'banana';

examples/module_mock/package.json

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+{
+  "devDependencies": {
+    "babel-preset-env": "*",
+    "jest": "*"
+  },
+  "scripts": {
+    "test": "jest"
+  }
+}