tictactoe/test/WinCheckerTests.java

import model.Board;
import model.IllegalGameStateException;
import model.Player;
import model.WinChecker;
import org.junit.jupiter.api.Assertions;
import org.junit.jupiter.api.Test;
import org.junit.jupiter.params.ParameterizedTest;
import org.junit.jupiter.params.provider.Arguments;
import org.junit.jupiter.params.provider.MethodSource;

import java.util.Random;
import java.util.stream.Stream;

public class WinCheckerTests {
    private final static Random rng = new Random();

    public static Stream<Arguments> isGameOverTestData() {
        Board randomBoard = new Board();
        Player currentBox;
        for (int i = 1; i <= 3; ++i)
            for (int j = 1; j <= 3; ++j) {
                int rand = rng.nextInt(3);
                Player p = switch (rand){
                    case 1 -> Player.X;
                    case 2 -> Player.O;
                    default -> null;
                };
                randomBoard.setBox(i, j, p);
            }

        boolean expected = false;

        currentBox = randomBoard.getBox(1, 1);
        if(currentBox != null){
            if (currentBox == randomBoard.getBox(1, 2) && currentBox == randomBoard.getBox(1, 3))
                expected = true;
            if (currentBox == randomBoard.getBox(2, 2) && currentBox == randomBoard.getBox(3, 3))
                expected = true;
            if (currentBox == randomBoard.getBox(2, 1) && currentBox == randomBoard.getBox(3, 1))
                expected = true;
        }

        currentBox = randomBoard.getBox(2, 1);
        if(currentBox != null && currentBox == randomBoard.getBox(2, 2) && currentBox == randomBoard.getBox(2, 3)){
            expected = true;
        }

        currentBox = randomBoard.getBox(3, 1);
        if(currentBox != null){
            if (currentBox == randomBoard.getBox(1, 3) && currentBox == randomBoard.getBox(2, 2)) {
                expected = true;
            }
            if (currentBox == randomBoard.getBox(3, 2) && currentBox == randomBoard.getBox(3, 3)) {
                expected = true;
            }
        }

        currentBox = randomBoard.getBox(1, 2);
        if(currentBox != null && currentBox == randomBoard.getBox(2, 2) && currentBox == randomBoard.getBox(3, 2)){
            expected = true;
        }

        currentBox = randomBoard.getBox(1, 3);
        if(currentBox != null && currentBox == randomBoard.getBox(2, 3) && currentBox == randomBoard.getBox(3, 3)){
            expected = true;
        }

        return Stream.of(
                Arguments.of(new Board(), false),
                Arguments.of(topRowXWins(), true),
                Arguments.of(midRowOWins(), true),
                Arguments.of(bottomRow(), true),
                Arguments.of(leftColumn(), true),
                Arguments.of(midColumn(), true),
                Arguments.of(rightColumn(), true),
                Arguments.of(diagUp(), true),
                Arguments.of(diagDown(), true),
                Arguments.of(stalemate(), true),
                Arguments.of(randomBoard, expected)
        );
    }

    private static Board stalemate() {
        Board b = new Board();
        b.setBox(1, 1, Player.X);
        b.setBox(1, 2, Player.O);
        b.setBox(1, 3, Player.X);
        b.setBox(2, 1, Player.O);
        b.setBox(2, 2, Player.O);
        b.setBox(2, 3, Player.X);
        b.setBox(3, 1, Player.X);
        b.setBox(3, 2, Player.X);
        b.setBox(3, 3, Player.O);
        return b;
    }

    private static Board diagDown() {
        Board b = new Board();
        b.setBox(3, 1, Player.O);
        b.setBox(2, 2, Player.O);
        b.setBox(1, 3, Player.O);
        return b;
    }

    private static Board diagUp() {
        Board b = new Board();
        b.setBox(1, 1, Player.O);
        b.setBox(2, 2, Player.O);
        b.setBox(3, 3, Player.O);
        return b;
    }

    private static Board rightColumn() {
        Board b = new Board();
        b.setBox(3, 1, Player.X);
        b.setBox(3, 2, Player.X);
        b.setBox(3, 3, Player.X);
        return b;
    }

    private static Board midColumn() {
        Board b = new Board();
        b.setBox(2, 1, Player.O);
        b.setBox(2, 2, Player.O);
        b.setBox(2, 3, Player.O);
        return b;
    }

    private static Board leftColumn() {
        Board b = new Board();
        b.setBox(1, 1, Player.O);
        b.setBox(1, 2, Player.O);
        b.setBox(1, 3, Player.O);
        return b;
    }

    private static Board bottomRow() {
        Board b = new Board();
        b.setBox(1, 3, Player.X);
        b.setBox(2, 3, Player.X);
        b.setBox(3, 3, Player.X);
        return b;
    }

    private static Board midRowOWins() {
        Board b = new Board();
        b.setBox(1, 2, Player.O);
        b.setBox(2, 2, Player.O);
        b.setBox(3, 2, Player.O);
        return b;
    }

    private static Board topRowXWins() {
        Board b = new Board();
        b.setBox(1, 1, Player.X);
        b.setBox(2, 1, Player.X);
        b.setBox(3, 1, Player.X);
        return b;
    }

    public static Stream<Arguments> getWinnerTestNormalData() {
        return Stream.of(
                Arguments.of(new Board(), null),
                Arguments.of(stalemate(), null),
                Arguments.of(topRowXWins(), Player.X),
                Arguments.of(midRowOWins(), Player.O)
        );
    }

    @ParameterizedTest
    @MethodSource("isGameOverTestData")
    public void isGameOverTest(Object[] args){
        Board b = (Board) args[0];
        boolean expected = (boolean) args[1];
        boolean actual = new WinChecker().isGameOver(b);
        Assertions.assertEquals(expected, actual);
    }

    @ParameterizedTest
    @MethodSource("getWinnerTestNormalData")
    public void getWinnerTestNormal(Object[] args){
        Board b = (Board) args[0];
        Player expected = (Player) args[1];
        Player actual = new WinChecker().getWinner(b);
        Assertions.assertEquals(expected, actual);
    }

    @Test
    public void getWinnerTestThrows(){
        Board b = new Board();
        b.setBox(1, 1, Player.X);
        b.setBox(1, 2, Player.X);
        b.setBox(1, 3, Player.X);
        b.setBox(2, 1, Player.O);
        b.setBox(2, 2, Player.O);
        b.setBox(2, 3, Player.O);
        Assertions.assertThrows(IllegalGameStateException.class, () -> new WinChecker().getWinner(b));
    }

    @Test
    public void getWinnerTestRandom(){
        Player currentBox;
        Board b = new Board();
        Player expected = null;
        boolean shouldThrow = false;

        for (int i = 1; i <= 3; ++i)
            for (int j = 1; j <= 3; ++j) {
                int rand = rng.nextInt(3);
                Player p = switch (rand){
                    case 1 -> Player.X;
                    case 2 -> Player.O;
                    default -> null;
                };
                b.setBox(i, j, p);
            }

        currentBox = b.getBox(1, 1);
        if(currentBox != null){
            if (currentBox == b.getBox(1, 2) && currentBox == b.getBox(1, 3))
                expected = currentBox;
            if (currentBox == b.getBox(2, 2) && currentBox == b.getBox(3, 3))
                expected = currentBox;
            if (currentBox == b.getBox(2, 1) && currentBox == b.getBox(3, 1))
                expected = currentBox;
        }

        currentBox = b.getBox(2, 1);
        if(currentBox != null && currentBox == b.getBox(2, 2) && currentBox == b.getBox(2, 3)){
            if (expected == null) expected = currentBox;
            else if (expected != currentBox) shouldThrow = true;
        }

        currentBox = b.getBox(3, 1);
        if(currentBox != null && !shouldThrow){
            if (currentBox == b.getBox(1, 3) && currentBox == b.getBox(2, 2)) {
                if (expected == null) expected = currentBox;
                else if (expected != currentBox) shouldThrow = true;
            }
            if (currentBox == b.getBox(3, 2) && currentBox == b.getBox(3, 3)) {
                if (expected == null) expected = currentBox;
                else if (expected != currentBox) shouldThrow = true;
            }
        }

        currentBox = b.getBox(1, 2);
        if(!shouldThrow && currentBox != null && currentBox == b.getBox(2, 2) && currentBox == b.getBox(3, 2)){
            if (expected == null) expected = currentBox;
            else if (expected != currentBox) shouldThrow = true;
        }

        currentBox = b.getBox(1, 3);
        if(!shouldThrow && currentBox != null && currentBox == b.getBox(2, 3) && currentBox == b.getBox(3, 3)){
            if (expected == null) expected = currentBox;
            else if (expected != currentBox) shouldThrow = true;
        }

        if (shouldThrow) Assertions.assertThrows(IllegalGameStateException.class, () -> new WinChecker().getWinner(b));
        else Assertions.assertEquals(expected, new WinChecker().getWinner(b));
    }
}