Being a fan of the TV show 'Sherlock', I had to play this game. This is my first Sherlock Holmes game and I was pleasantly surprised. The Testament of Sherlock Holmes is a point-and-click adventure game where you play as Sherlock (and Watson) trying to resolve the murder of a Reverend in his own church. I won't say more about the story since the main reason of playing this game is to discover that.
The gameplay is faily simple. Where you can interact, there is either a magnifying glass to look at some items or a hand to show that you can take the item or that you can interact with it. That's it. Most of the time, you'll have to look through everything to be sure that you didn't miss any important clue. The rooms are small enough so it's really easy to find everything.
Also, as a detective, there is a deduction board. You'll have to discover every clues to see statements about them. With these facts, it's up to you to choose between 3 answers which one is the right one about what happened in this case. There are multiple questions to be answered and you won't know if you're right until you have all the right answers. It can be hard but if you pay attention to the story, it will be fairly easy. There is also a lot of puzzles in this game. Some are logic and really easy once you understand how they work but some of the puzzles that does NOT involve any deduction/logic can be really hard and frustrating for some people. There is a skip buttons after some minutes so don't worry !
One of the problem in this game is that it's too linear for a detective game. There is no real choice to be made and even if you choose to go to a location instead of another, you'll end up going to both places without any change.
The story is really interesting and there are a lot of twists (I found it similar to the TV show and it's a good thing). The problem (because it's a videogame !) is that Sherock is not as funny as Cumberbatch's Sherlock (but it's understandable since there is no actor involved).
In conclusion, if you like point-and-click games, you'll like this one. It will definitely entertain you for hours ! (I finished the game in about 7-8 hours)