diff --git a/src/components/board/__tests__/board-renderer.test.ts b/src/components/board/__tests__/board-renderer.test.ts
new file mode 100644
index 0000000..23500b5
--- /dev/null
+++ b/src/components/board/__tests__/board-renderer.test.ts
@@ -0,0 +1,63 @@
+import { describe, it, expect } from 'vitest';
+import {
+  computeBoardDimensions,
+  canvasToBoard,
+  boardToCanvas,
+  computeStarPoints,
+} from '../board-renderer';
+
+describe('computeBoardDimensions', () => {
+  it('returns positive cellSize and padding for 15x15 board', () => {
+    const cfg = computeBoardDimensions(15, 800, 600);
+    expect(cfg.cellSize).toBeGreaterThan(0);
+    expect(cfg.padding).toBeGreaterThan(0);
+    expect(cfg.boardSize).toBe(15);
+  });
+
+  it('fits within the smaller canvas dimension', () => {
+    const cfg = computeBoardDimensions(15, 800, 600);
+    const total = cfg.padding * 2 + (cfg.boardSize - 1) * cfg.cellSize;
+    expect(total).toBeLessThanOrEqual(800);
+  });
+});
+
+describe('canvasToBoard / boardToCanvas round-trip', () => {
+  it('round-trips for a 15x15 board center', () => {
+    const cfg = computeBoardDimensions(15, 800, 600);
+    const boardPos = { x: 7, y: 7 };
+    const canvas = boardToCanvas(boardPos, cfg);
+    const restored = canvasToBoard(canvas.x, canvas.y, cfg);
+    expect(restored).toEqual(boardPos);
+  });
+
+  it('returns null for clicks outside the board', () => {
+    const cfg = computeBoardDimensions(15, 800, 600);
+    expect(canvasToBoard(-10, -10, cfg)).toBeNull();
+    expect(canvasToBoard(9999, 9999, cfg)).toBeNull();
+  });
+});
+
+describe('computeStarPoints', () => {
+  it('returns 9 star points for 15x15 board', () => {
+    const points = computeStarPoints(15);
+    expect(points.length).toBe(9);
+  });
+
+  it('returns only center for board smaller than 9', () => {
+    const points = computeStarPoints(7);
+    expect(points.length).toBe(1);
+    expect(points[0]).toEqual([3, 3]);
+  });
+
+  it('star points are within board bounds', () => {
+    for (const size of [9, 13, 15, 19]) {
+      const points = computeStarPoints(size);
+      for (const [r, c] of points) {
+        expect(r).toBeGreaterThanOrEqual(0);
+        expect(r).toBeLessThan(size);
+        expect(c).toBeGreaterThanOrEqual(0);
+        expect(c).toBeLessThan(size);
+      }
+    }
+  });
+});
diff --git a/src/core/__tests__/types.test.ts b/src/core/__tests__/types.test.ts
new file mode 100644
index 0000000..1c15884
--- /dev/null
+++ b/src/core/__tests__/types.test.ts
@@ -0,0 +1,38 @@
+import { describe, it, expect } from 'vitest';
+
+describe('types', () => {
+  it('CellState values are correct', () => {
+    const empty: number = 0;
+    const black: number = 1;
+    const white: number = 2;
+    expect(empty).toBe(0);
+    expect(black).toBe(1);
+    expect(white).toBe(2);
+  });
+
+  it('MoveResult has correct shape', () => {
+    const result = {
+      position: { x: 7, y: 7 },
+      is_win: false,
+      is_forbidden: false,
+    };
+    expect(result.position.x).toBe(7);
+    expect(result.is_win).toBe(false);
+  });
+
+  it('GameConfig has all required fields with defaults', () => {
+    const config = {
+      boardSize: 15,
+      useForbiddenRules: true,
+      useTimer: false,
+      timeLimitSecs: 60,
+      aiDifficulty: 3,
+      playerColor: 'Black' as const,
+      isServer: false,
+      remoteAddress: '',
+    };
+    expect(config.boardSize).toBeGreaterThanOrEqual(9);
+    expect(config.boardSize).toBeLessThanOrEqual(19);
+    expect(['Black', 'White']).toContain(config.playerColor);
+  });
+});