Copy in integrations tests from pull jestjs#5241

Done at the request of @SimenB from PR jestjs#5972

integration-tests/__tests__/module_parent_null_in_test.js

@@ -0,0 +1,17 @@
+/**
+ * Copyright (c) 2014-present, Facebook, Inc. All rights reserved.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow
+ */
+'use strict';
+
+const runJest = require('../runJest');
+
+test('module.parent should be null in test files', () => {
+  const {status} = runJest('module_parent_null_in_test');
+
+  expect(status).toBe(0);
+});

integration-tests/module_parent_null_in_test/__tests__/index.js

@@ -0,0 +1,13 @@
+/**
+ * Copyright (c) 2014-present, Facebook, Inc. All rights reserved.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+'use strict';
+
+test('moduleNameMapping wrong configuration', () => {
+  expect(module).not.toBe(module.parent);
+  expect(module.parent).toBeNull();
+});

integration-tests/module_parent_null_in_test/package.json

@@ -0,0 +1,3 @@
+{
+  "jest": {}
+}