Run npm start and test the es5 build. This will internally run ng build and then start a http-server to deliver the dist folder

Instead if an array of numbers, it contains an empty object

The ES2015 build shows:

 {
  "shouldContain1234": [
    1,
    2,
    3,
    4
  ],
  "shouldContain567": [
    5,
    6,
    7
  ]
} 

Ths ES5 build shows:

 {
  "shouldContainer1234": [
    {}
  ],
  "shouldContainen567": [
    {}
  ]
}