Add a gulp script for extracting error codes (#6882)

scripts/error-codes/__tests__/invertObject-test.js

@@ -0,0 +1,54 @@
+/**
+ * Copyright (c) 2013-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';
+
+var invertObject = require('../invertObject');
+
+var objectValues = (target) => Object.keys(target).map((key) => target[key]);
+
+describe('invertObject', () => {
+  it('should return an empty object for an empty input', () => {
+    expect(invertObject({})).toEqual({});
+  });
+
+  it('should invert key-values', () => {
+    expect(invertObject({
+      a: '3',
+      b: '4',
+    })).toEqual({
+      3: 'a',
+      4: 'b',
+    });
+  });
+
+  it('should take the last value when there\'re duplications in vals', () => {
+    expect(invertObject({
+      a: '3',
+      b: '4',
+      c: '3',
+    })).toEqual({
+      4: 'b',
+      3: 'c',
+    });
+  });
+
+  it('should perserve the original order', () => {
+    expect(Object.keys(invertObject({
+      a: '3',
+      b: '4',
+      c: '3',
+    }))).toEqual(['3', '4']);
+
+    expect(objectValues(invertObject({
+      a: '3',
+      b: '4',
+      c: '3',
+    }))).toEqual(['c', 'b']);
+  });
+});