diff --git a/src/components/Highlight.test.tsx b/src/components/Highlight.test.tsx
new file mode 100644
index 0000000..5d1fbc3
--- /dev/null
+++ b/src/components/Highlight.test.tsx
@@ -0,0 +1,15 @@
+import { render } from '@testing-library/react'
+import React, { ComponentProps } from 'react'
+import { Highlight } from './Highlight'
+
+function test(title: string, text: string, match?: ComponentProps<typeof Highlight>['match']) {
+  it(title, () => {
+    expect(render(<Highlight text={text} match={match} />).container.textContent).toBe(text)
+  })
+}
+
+test('sample', 'abc', undefined)
+test('sample', 'abc', /./)
+test('sample', 'abc', /../)
+test('sample', 'abc', /.../)
+test('sample', 'abc', /..../)
diff --git a/src/components/Highlight.tsx b/src/components/Highlight.tsx
index cb91e29..0102ef7 100644
--- a/src/components/Highlight.tsx
+++ b/src/components/Highlight.tsx
@@ -1,17 +1,11 @@
-import * as React from 'react'
+import * as React from 'react';
 
-export const Highlight = React.memo(function Highlight(props: {
-  text: string
-  match?: RegExp | string
-}) {
+export const Highlight = React.memo(function Highlight(props: { text: string; match?: RegExp }) {
   const { text, match } = props
   const $match = React.useMemo(() => {
-    if (match) {
-      if (match instanceof RegExp) {
-        if (match.flags.includes('g')) return match
-        return new RegExp(match.source, 'g' + match.flags)
-      }
-      return new RegExp(match, 'g')
+    if (match instanceof RegExp) {
+      if (match.flags.includes('g')) return match
+      return new RegExp(match.source, 'g' + match.flags)
     }
     return null
   }, [match])