diff --git a/src/modules/picture.js b/src/modules/picture.js
index a65e566..117d358 100644
--- a/src/modules/picture.js
+++ b/src/modules/picture.js
@@ -40,7 +40,7 @@ export function picToBoard(pixels, board) {
   const flat = pixels.reduce((acc, pixel, index) => {
     const i = index * 4;
     const count = pixels[i] + pixels[i + 1] + pixels[i + 2];
-    const value = count >= 255 ? 1 : 0;
+    const value = (count >= 255) & 1;
     acc[index] = value;
     return acc;
   }, []);
@@ -58,8 +58,7 @@ export function boardToPic(board) {
   const img = new ImageData(board.width, board.height);
   const colors = [hexToRGB(live), hexToRGB(dead)];
   board.grid.flat().reduce((acc, cell, index) => {
-    // TODO : bitshift operation instead of ternary
-    const color = cell === 1 ? colors[0] : colors[1];
+    const color = colors[(cell === 1) & 1];
     const i = index * 4;
     acc[i] = color[0];
     acc[i + 1] = color[1];
diff --git a/tests/core.test.js b/tests/core.test.js
new file mode 100644
index 0000000..355865b
--- /dev/null
+++ b/tests/core.test.js
@@ -0,0 +1,18 @@
+import { describe, expect, test } from "vitest";
+import { evolve1d, create1dStateOneCell } from "src/modules/core.js";
+import { presetRuleset } from "src/modules/preset.js";
+
+describe("Core", () => {
+  test("evolve1d, rules73, 9 cells", () => {
+    const state = [0, 0, 0, 0, 1, 0, 0, 0, 0];
+    const got = evolve1d(state, presetRuleset[0].rules);
+    const valid = [1, 1, 1, 0, 0, 0, 1, 1, 1];
+    expect(got.length).toBe(state.length);
+    expect(got).toEqual(valid);
+  }),
+    test("create1dStateOneCell, 49 cells", () => {
+      const got = create1dStateOneCell(49);
+      expect(got.length).toBe(49);
+      expect(got[24]).toBe(1);
+    });
+});