diff --git a/src/index.test.js b/src/index.test.js
new file mode 100644
index 0000000..e655888
--- /dev/null
+++ b/src/index.test.js
@@ -0,0 +1,26 @@
+const assert = require('node:assert/strict');
+const { spawnSync } = require('node:child_process');
+const path = require('node:path');
+const test = require('node:test');
+
+test('主流程失敗時會輸出階段前綴與錯誤碼', () => {
+  const result = spawnSync(
+    process.execPath,
+    [path.join(__dirname, 'index.js')],
+    {
+      cwd: path.join(__dirname, '..'),
+      env: {
+        ...process.env,
+        GITEA_SERVER_URL: '',
+        GITEA_REPOSITORY: 'owner/repo',
+        RUNNER_TOKEN: 'token',
+        IS_BETA: 'false',
+      },
+      encoding: 'utf8',
+    },
+  );
+
+  assert.equal(result.status, 1);
+  assert.match(result.stderr, /^\[參數檢查\]\[ERR\]\[\d{4}\/\d{2}\/\d{2} /);
+  assert.match(result.stderr, /GITEA_SERVER_URL 未設定/);
+});