diff --git a/package.json b/package.json
index 6395d43..7156375 100644
--- a/package.json
+++ b/package.json
@@ -3,6 +3,7 @@
   "description": "namae saves your time searching around registries and checking if the desired name is ready for use.",
   "author": "Yasuaki Uechi <y@uechi.io> (https://uechi.io/)",
   "scripts": {
+    "dev": " yarn start",
     "postinstall": "yarn --cwd web && yarn --cwd api",
     "ship": "now",
     "start": "now dev",
diff --git a/web/src/util/hooks.test.tsx b/web/src/util/hooks.test.tsx
new file mode 100644
index 0000000..38a737b
--- /dev/null
+++ b/web/src/util/hooks.test.tsx
@@ -0,0 +1,20 @@
+import React from 'react';
+import {render, waitForDomChange} from '@testing-library/react';
+import {useDeferredState} from './hooks';
+
+const App: React.FC = () => {
+  const [value, setValue] = useDeferredState(500, 0);
+  React.useEffect(() => {
+    setValue(1);
+    setValue(2);
+    setValue(3);
+  }, [setValue]);
+  return <div data-testid="root">{value}</div>;
+};
+
+it('provoke state flow after certain time passed', async () => {
+  const {container, getByTestId} = render(<App />);
+  expect(getByTestId('root').textContent).toBe('0');
+  await waitForDomChange({container});
+  expect(getByTestId('root').textContent).toBe('3');
+});
diff --git a/web/src/util/pwa.test.ts b/web/src/util/pwa.test.ts
new file mode 100644
index 0000000..8163448
--- /dev/null
+++ b/web/src/util/pwa.test.ts
@@ -0,0 +1,5 @@
+import {isStandalone} from './pwa';
+
+it('recognize standalone mode', () => {
+  expect(isStandalone()).toEqual(false);
+});
diff --git a/web/src/util/text.test.ts b/web/src/util/text.test.ts
new file mode 100644
index 0000000..22899cb
--- /dev/null
+++ b/web/src/util/text.test.ts
@@ -0,0 +1,9 @@
+import {capitalize} from './text';
+
+it('capitalize text', () => {
+  expect(capitalize('test')).toEqual('Test');
+  expect(capitalize('Test')).toEqual('Test');
+  expect(capitalize('tEST')).toEqual('Test');
+  expect(capitalize('TEST')).toEqual('Test');
+  expect(capitalize('')).toEqual('');
+});
diff --git a/web/src/util/text.ts b/web/src/util/text.ts
index b66512c..84302a4 100644
--- a/web/src/util/text.ts
+++ b/web/src/util/text.ts
@@ -1,3 +1,4 @@
 export function capitalize(text: string) {
+  if (text.length === 0) return '';
   return text[0].toUpperCase() + text.slice(1).toLowerCase();
 }