Add test case for the issue exceljs#257

Author: Olivier Robin

spec/integration/data/test-issue-257.xlsx

@@ -0,0 +1,18 @@
+'use strict';
+
+var chai = require('chai');
+var verquire = require('../../utils/verquire');
+
+var Excel = verquire('excel');
+
+var expect = chai.expect;
+
+describe('github issues', function() {
+  it('issue 257 - worksheet order is not respected', function() {
+    var wb = new Excel.Workbook();
+    return wb.xlsx.readFile('./spec/integration/data/test-issue-257.xlsx')
+      .then(function() {
+        expect(wb.worksheets.map(ws => ws.name)).to.deep.equal(['First', 'Second']);
+      });
+  });
+});