We had to use toLocaleString with a specific country-code. toLocaleString('de'). This works perfectly in all the browsers. However, not in jest tests.
Our Jest tests were running with --env=jsdom. I got to know that jsdom and phantomJS aren't supporting multiple locale implementations.PhantomJS support locale-specific.
So, the only solution I found is to mock these methods and test rest of the logic. Here is a sample mock behaviour.
Note: This behaviour is applicable for toLocaleDateString() toLocaleTimeString()