diff --git a/logic/board.ts b/logic/board.ts
index eaa8d61..0d4c225 100644
--- a/logic/board.ts
+++ b/logic/board.ts
@@ -8,9 +8,13 @@ import type {
 import { createSection } from "./section.ts";
 
 export function createBoard(config: BoardConfig): BoardData {
-  const sections: SectionData[][] = Array(config.ySections).map((_, sy) =>
-    Array(config.xSections).map((_, sx) => createSection({ sx, sy }, config))
-  );
+  const sections: SectionData[][] = Array(config.ySections)
+    .fill(0)
+    .map((_, sy) =>
+      Array(config.xSections)
+        .fill(0)
+        .map((_, sx) => createSection({ sx, sy }, config))
+    );
 
   return { config, sections };
 }
diff --git a/tests/board.test.ts b/tests/board.test.ts
new file mode 100644
index 0000000..dc85e66
--- /dev/null
+++ b/tests/board.test.ts
@@ -0,0 +1,45 @@
+import {
+  assert,
+  assertEquals,
+} from "https://deno.land/std@0.224.0/assert/mod.ts";
+
+import { createBoard, renderFullBoard } from "../logic/board.ts";
+import { BoardData } from "../mod.ts";
+import { checkFullBoard } from "./checkFullBoard.ts";
+
+Deno.test("board", async (t) => {
+  let board: BoardData | undefined;
+
+  await t.step("createBoard", () => {
+    board = createBoard({
+      xSections: 2,
+      ySections: 2,
+      sectionWidth: 4,
+      sectionHeight: 3,
+      defaultCh: " ",
+      defaultColor: "F",
+      defaultBgColor: "0",
+      defaultWidth: 1,
+    });
+
+    assertEquals(board.sections.length, 2);
+    assertEquals(board.sections[0].length, 2);
+    assertEquals(board.sections[0][0].offsetX, 0);
+    assertEquals(board.sections[0][0].offsetY, 0);
+    assertEquals(board.sections[0][1].offsetX, 4);
+    assertEquals(board.sections[0][1].offsetY, 0);
+    assertEquals(board.sections[1].length, 2);
+    assertEquals(board.sections[1][0].offsetX, 0);
+    assertEquals(board.sections[1][0].offsetY, 3);
+    assertEquals(board.sections[1][1].offsetX, 4);
+    assertEquals(board.sections[1][1].offsetY, 3);
+  });
+
+  await t.step("renderFullBoard", () => {
+    assert(board);
+
+    const rendered = renderFullBoard(board);
+
+    checkFullBoard(rendered);
+  });
+});
diff --git a/tests/checkFullBoard.ts b/tests/checkFullBoard.ts
new file mode 100644
index 0000000..3a8d8af
--- /dev/null
+++ b/tests/checkFullBoard.ts
@@ -0,0 +1,98 @@
+import { getCharacterWidth } from "../logic/character.ts";
+import { FullBoard } from "../types/board.ts";
+
+function isCorrectWidth(cWdRaw: string, cCh: string): boolean {
+  return getCharacterWidth(cCh).toString() === cWdRaw;
+}
+
+function isValidColor(color: string): boolean {
+  return /^[0-9A-F]$/.test(color);
+}
+
+export function checkFullBoard(board: FullBoard) {
+  let chLine = "";
+  let colorLine = "";
+  let bgColorLine = "";
+  let widthLine = "";
+  let lines = 0;
+  const ch = [...board.ch];
+  const chLength = ch.length;
+
+  let unsafeCurrentOffset = 0;
+
+  for (let i = 0; i < chLength; i++) {
+    const cCh = ch[i];
+    const cCo = board.color[i];
+    const cBg = board.bg_color[i];
+    const cWdRaw = board.width[i];
+    const cWd = parseInt(cWdRaw);
+
+    const printSituation = () => {
+      console.error(
+        "offset:",
+        i,
+        "offset (unsafe):",
+        unsafeCurrentOffset,
+        "cCh:",
+        JSON.stringify(cCh),
+        "cCo:",
+        JSON.stringify(cCo),
+        "cBg:",
+        JSON.stringify(cBg),
+        "cWd:",
+        JSON.stringify(cWdRaw),
+      );
+      console.error("ch:      ", chLine);
+      console.error("color:   ", colorLine);
+      console.error("bg_color:", bgColorLine);
+      console.error("width:   ", widthLine);
+    };
+
+    if (cCh === "\n") {
+      if (cCo !== "\n" || cBg !== "\n" || cWdRaw !== "\n") {
+        printSituation();
+        throw new Error("cCh is newline while at least one other field aren't");
+      }
+
+      if (colorLine.length !== board.w) {
+        printSituation();
+        throw new Error("color line length error");
+      }
+      if (bgColorLine.length !== board.w) {
+        printSituation();
+        throw new Error("bg color line length error");
+      }
+      if (widthLine.length !== board.w) {
+        printSituation();
+        throw new Error("width line length error");
+      }
+
+      chLine = "";
+      colorLine = "";
+      bgColorLine = "";
+      widthLine = "";
+      lines++;
+      unsafeCurrentOffset += cCh.length;
+
+      continue;
+    }
+
+    if (!isValidColor(cCo) || !isValidColor(cBg)) {
+      printSituation();
+      throw new Error("cCo or cBg is not valid");
+    }
+
+    if (!isCorrectWidth(cWdRaw, cCh)) {
+      printSituation();
+      throw new Error("cWd is wrong");
+    }
+
+    chLine += cCh;
+    colorLine += cCo.padEnd(cWd);
+    bgColorLine += cBg.padEnd(cWd);
+    widthLine += cWdRaw.padEnd(cWd);
+    unsafeCurrentOffset += cCh.length;
+  }
+
+  if (lines + 1 !== board.h) throw new Error("board height error");
+}