Paris - Virat Kohli's India dominated 2017 in Test cricket as they shored up top spot in the rankings, but will face far tougher challenges in South Africa and England next year while Afghanistan and Ireland start a new Test era.
The 29-year-old Kohli racked up three double hundreds as his team extended their winning streak to nine Test series as Bangladesh and Australia were beaten, with Sri Lanka seen off home and away.
India have never won in South Africa, though, while the two-time World Cup champions were well beaten on their last two visits to England - 3-1 in 2015 and 4-0 in 2011.
But this is a fantastic side that many have hailed as India's greatest ever, with Kohli, Cheteshwar Pujara and Murali Vijay piling on the runs and spinners Ravichandran Ashwin and Ravindra Jadeja wreaking havoc.
Despite sitting second in the rankings, South Africa are not the force they once were and lost at home to a Ben Stokes-inspired England in 2016, while Joe Root's men showed plenty of cracks in their armour during the meek surrender of the Ashes Down Under.
Until last week Kohli held both the number one spot in the ODI and Twenty20 batting rankings, and has developed into one of the best young Test captains in the world, at a time when 26-year-old Root and Australia's Steve Smith, 28, have also taken charge of their countries.
"I'd say Virat is one of the best captains at the moment, the most improved - there's a big change from when I first saw him captaining to now," said Proteas batsman AB de Villiers ahead of their first Test against India in Cape Town on January 5.
On a personal level, though, the biggest tour of 2018 for Kohli will be when he takes his team to England for a Test series in August.
Despite having scored three hundreds against England in two home series, Kohli had possibly his worst ever tour when he visited the UK three years ago.
He struggled with the swinging and seaming conditions, managing a top score of just 39 in five Tests with an paltry average of 13.4 and will be desperate to put that right.
One eye might be on the second Test at Lord's, where Kohli could endear himself even more to his legions of fans by scoring a hundred at a ground where even Sachin Tendulkar failed to get on the honours board.
Cricket's most exclusive club was finally expanded for the first time since Bangladesh joined in 1999, as Ireland and Afghanistan were awarded Test status in June.
For Ireland, it is reward for a long period of consistency that has brought them World Cup wins over Pakistan 10 years ago, England in stunning fashion four years later, and the West Indies in 2015.
War-torn Afghanistan's rise has been quicker, but they cemented their status as the best nation outside of Test cricket and have a promising future with a talented bowling attack led by 19-year-old sensation Rashid Khan.
Khan has produced eye-catching performances in the world's top T20 leagues, most recently with a man-of-the-match display on his Big Bash debut for the Adelaide Strikers.
"I play cricket to bring victories for my country and to make Afghanistan proud on the world stage," Khan told AFP in an interview in October.
Ireland, who will play their maiden Test against Pakistan at Malahide in May, surprisingly beat Afghanistan in an ODI series earlier this month to give themselves a lift.
Afghanistan will play their first Test match against India, where they play the majority of their home games, although a date is yet to be announced.