The summary of all the Tests played in the calendar year 2019. Here the teams are ranked by win/loss ratio. India is at the top with 7 wins and no losses, while Ireland and Bangladesh lost all their matches. Australia and Afghanistan (!) are next to India. Zimbabwe did not play any Test in this year, though they will resume in January 2020.
The ICC ranking tables at the end of the year are more meaningful:
A more realistic assessment, with Afghanistan overtaking Zimbabwe besides Ireland.
According to this, New Zealand is India’s closest rival with South Africa, England and Australia in joint third position (though they are actually separated by small fractions).
Then there is the new contest, the World Test Championship. Not all Test countries are involved. Even among the 9 countries involved, not all Test series are counted. An example is the 2-Test tour of England to New Zealand. This was the WTC points table at the end of the year:
It is still at an early stage, but it does seem that the other teams will not find it easy to catch up with India and Australia. By the middle of January, Australia had moved up to 296 and England to 86.