tic-tac-toe-game | classic game of Tic Tac Toe | Game Engine library

I have not seen module used like that within spec files. I suspect that's a very old tutorial. (Wordpress helpfully shows it's from Oct 25, but neglects to mention which year. But the oldest comment is from 2014)

I recommend you find a more recent tutorial.

The describe keyword would be more appropriate here. Most of the specs I work with looked like this a few years ago:

If you are using a minimax strategy to play tic-tac-toe, you can have multiple switch cases that correspond to different difficulty levels in the game. The most naive method of doing this is by putting different depth thresholds in the minimax tree. For example, you can expand the minimax game tree until only depth 2 (assuming for a 3*3 tic-tac-toe) for easy level and say until the end of the search tree for the highest difficulty level. You can set this threshold depending on the board size and the difficulty level expected.

Another way of implementing difficulty levels is by implementing different heuristic functions to calculate the board score (a goodness measure to the current state of the board). You can have your heuristic function that evaluates the individual row/column/diagonal score based on the number of cells that you occupy in that row/column/diagonal. For example, if the number of cells occupied is 1, then score = x (x can be any arbitrary number). If the number of cells occupied is 2, then score = x^2 and if it is 3, then score = x^3. Then multiply all individual line scores to get a measure of goodness (or you can think of this as a winning probability) in each row, column or diagonal. You can calculate a similar score for your opponent and then take a difference to get a board score. Thus the idea is to implement different ways of evaluating current board states by designing different variations of the heuristic function for each difficulty level. A bad heuristic function would work as an easy level since it will lose a lot of games whereas a properly designed heuristic will have a no-lose policy (it will end up winning or drawing the game).

In order to randomly choose a difficulty level at each run of the game, you can use a random number generator to pick a difficulty level. You can assign '0' as easy, '1' as medium and '2' as hard. You can use the following java function to generate an integer between 0 and (n-1)

int random = Random.nextInt(n)

The single method you want to use should look like this: