diff --git a/src/test/java/HitoriGameSolverTest.java b/src/test/java/HitoriGameSolverTest.java
new file mode 100644
index 0000000..15a0487
--- /dev/null
+++ b/src/test/java/HitoriGameSolverTest.java
@@ -0,0 +1,127 @@
+import domain.GameSolver;
+import org.junit.jupiter.api.*;
+import static org.junit.jupiter.api.Assertions.*;
+import java.util.List;
+
+class HitoriGameSolverTest {
+    private GameSolver game;
+    private static final int[][] TEST_BOARD = {
+            {1, 2, 1},
+            {2, 1, 2},
+            {1, 2, 1}
+    };
+
+    @BeforeEach
+    void setUp() {
+        game = new GameSolver(TEST_BOARD);
+    }
+
+    @Test
+    void testUnsolvedInitialState() {
+        assertFalse(game.isSolved());
+    }
+
+    @Test
+    void testSolvingPuzzle() {
+        // Apply known solution
+        game.markCellAsBlack(0, 2);
+        game.markCellAsWhite(0, 0);
+        game.markCellAsWhite(0, 1);
+        game.markCellAsWhite(1, 0);
+        game.markCellAsWhite(1, 1);
+        game.markCellAsWhite(1, 2);
+        game.markCellAsWhite(2, 0);
+        game.markCellAsWhite(2, 1);
+        game.markCellAsBlack(2, 2);
+
+        assertTrue(game.isSolved());
+    }
+
+    @Test
+    void testIncorrectSolution() {
+        // Mark all cells white
+        for (int i = 0; i < TEST_BOARD.length; i++) {
+            for (int j = 0; j < TEST_BOARD[0].length; j++) {
+                game.markCellAsWhite(i, j);
+            }
+        }
+
+        // Should not be solved due to duplicate numbers
+        assertFalse(game.isSolved());
+    }
+
+    @Test
+    void testDisconnectedWhiteCells() {
+        // Create a solution with disconnected white cells
+        game.markCellAsWhite(0, 0);
+        game.markCellAsBlack(0, 1);
+        game.markCellAsBlack(1, 0);
+        game.markCellAsBlack(1, 1);
+        game.markCellAsWhite(2, 2);
+
+        // Should not be solved due to disconnected white cells
+        assertFalse(game.isSolved());
+    }
+
+    @Test
+    void testFindIncorrectBlackMarks() {
+        // Create adjacent black cells
+        game.markCellAsBlack(0, 0);
+        game.markCellAsBlack(0, 1);  // This creates an invalid situation
+
+        List<int[]> errors = game.findIncorrectBlackMarks();
+        assertFalse(errors.isEmpty());
+        assertEquals(2, errors.size());  // Both cells should be reported
+
+        // Verify error coordinates
+        boolean foundFirst = false;
+        boolean foundSecond = false;
+        for (int[] error : errors) {
+            if (error[0] == 0 && error[1] == 0) foundFirst = true;
+            if (error[0] == 0 && error[1] == 1) foundSecond = true;
+        }
+        assertTrue(foundFirst && foundSecond);
+    }
+
+    @Test
+    void testNoIncorrectBlackMarks() {
+        // Make valid black marks
+        game.markCellAsBlack(0, 0);
+        game.markCellAsBlack(2, 2);
+
+        List<int[]> errors = game.findIncorrectBlackMarks();
+        assertTrue(errors.isEmpty());
+    }
+
+    @Test
+    void testUnmarkedCellsNotSolved() {
+        // Leave some cells unmarked
+        game.markCellAsWhite(0, 0);
+        game.markCellAsBlack(0, 1);
+        // Don't mark other cells
+
+        assertFalse(game.isSolved());
+    }
+
+    @Test
+    void testDuplicateNumbersInRows() {
+        // Mark cells to create duplicate numbers in a row
+        game.markCellAsWhite(0, 0);
+        game.markCellAsWhite(0, 1);
+        game.markCellAsWhite(0, 2);
+        // Row now has duplicate numbers
+
+        assertFalse(game.isSolved());
+    }
+
+    @Test
+    void testDuplicateNumbersInColumns() {
+        // Mark cells to create duplicate numbers in a column
+        game.markCellAsWhite(0, 0);
+        game.markCellAsWhite(1, 0);
+        game.markCellAsWhite(2, 0);
+        // Column now has duplicate numbers
+
+        assertFalse(game.isSolved());
+    }
+}