diff --git a/package.json b/package.json
index 869e8059..579876af 100644
--- a/package.json
+++ b/package.json
@@ -6,8 +6,9 @@
     "start": "node scripts/build.js copyFilesDev && node scripts/prepareData.mjs && node esbuild.mjs --watch",
     "start-watch-script": "nodemon -w esbuild.mjs esbuild.mjs",
     "build": "node scripts/build.js copyFiles && node scripts/prepareData.mjs -f && node esbuild.mjs --minify --prod",
-    "check-build": "tsc && pnpm build",
+    "check-build": "tsc && pnpm test-unit && pnpm build",
     "test:cypress": "cypress run",
+    "test-unit": "vitest",
     "test:e2e": "start-test http-get://localhost:8080 test:cypress",
     "prod-start": "node server.js",
     "postinstall": "node scripts/gen-texturepack-files.mjs && tsx scripts/optimizeBlockCollisions.ts",
diff --git a/prismarine-viewer/viewer/sign-renderer/index.ts b/prismarine-viewer/viewer/sign-renderer/index.ts
index 5471ccf4..b4200c5d 100644
--- a/prismarine-viewer/viewer/sign-renderer/index.ts
+++ b/prismarine-viewer/viewer/sign-renderer/index.ts
@@ -57,7 +57,8 @@ export const renderSign = (blockEntity: SignBlockEntity, PrismarineChat: typeof
     const defaultColor = ('front_text' in blockEntity ? blockEntity.front_text.color : blockEntity.Color) || 'black'
     for (let [lineNum, text] of texts.slice(0, 4).entries()) {
         // todo: in pre flatenning it seems the format was not json
-        const parsed = text?.startsWith('{') ? parseSafe(text ?? '""', 'sign text') : text
+        if (text === 'null') continue
+        const parsed = text?.startsWith('{') || text?.startsWith('"') ? parseSafe(text ?? '""', 'sign text') : text
         if (!parsed || (typeof parsed !== 'object' && typeof parsed !== 'string')) continue
         // todo fix type
         const message = typeof parsed === 'string' ? fromFormattedString(parsed) : new PrismarineChat(parsed) as never
diff --git a/prismarine-viewer/viewer/sign-renderer/tests.test.ts b/prismarine-viewer/viewer/sign-renderer/tests.test.ts
new file mode 100644
index 00000000..03eb4394
--- /dev/null
+++ b/prismarine-viewer/viewer/sign-renderer/tests.test.ts
@@ -0,0 +1,85 @@
+import { test, expect } from 'vitest'
+import { renderSign } from '.'
+import PrismarineChatLoader from 'prismarine-chat'
+
+const PrismarineChat = PrismarineChatLoader({ language: {} } as any)
+let ctxTexts = [] as any[]
+
+global.document = {
+  createElement () {
+    return {
+      getContext () {
+        return {
+          fillText (text, x, y) {
+            ctxTexts.push({ text, x, y })
+          },
+          measureText () { return 0 }
+        }
+      }
+    }
+  }
+} as any
+
+const render = (entity) => {
+  ctxTexts = []
+  renderSign(entity, PrismarineChat)
+  return ctxTexts.map(({ text, y }) => [y / 80, text])
+}
+
+test('sign renderer', () => {
+  let blockEntity = {
+    "GlowingText": 0,
+    "Color": "black",
+    "Text4": "{\"text\":\"\"}",
+    "Text3": "{\"text\":\"\"}",
+    "Text2": "{\"text\":\"\"}",
+    "Text1": "{\"extra\":[{\"color\":\"dark_green\",\"text\":\"Minecraft \"},{\"text\":\"Tools\"}],\"text\":\"\"}"
+  } as any
+  expect(render(blockEntity)).toMatchInlineSnapshot(`
+    [
+      [
+        1,
+        "",
+      ],
+      [
+        1,
+        "Minecraft ",
+      ],
+      [
+        1,
+        "Tools",
+      ],
+      [
+        2,
+        "",
+      ],
+      [
+        3,
+        "",
+      ],
+      [
+        4,
+        "",
+      ],
+    ]
+  `)
+
+  blockEntity = { // pre flatenning
+    "Text1": "Welcome to",
+    "Text2": "",
+    "Text3": "null",
+    "Text4": "\"Version 2.1\"",
+  } as const
+  expect(render(blockEntity)).toMatchInlineSnapshot(`
+    [
+      [
+        1,
+        "Welcome to",
+      ],
+      [
+        4,
+        "Version 2.1",
+      ],
+    ]
+  `)
+})
diff --git a/vitest.config.ts b/vitest.config.ts
new file mode 100644
index 00000000..7636f5e3
--- /dev/null
+++ b/vitest.config.ts
@@ -0,0 +1,10 @@
+import { defineConfig } from 'vitest/config'
+
+export default defineConfig({
+  root: 'prismarine-viewer/viewer',
+  test: {
+    include: [
+      '**/*.test.ts'
+    ],
+  },
+})