diff --git a/packages/vite-plugin-checker/__tests__/unit/__snapshots__/logger.spec.ts.snap b/packages/vite-plugin-checker/__tests__/unit/__snapshots__/logger.spec.ts.snap
new file mode 100644
index 00000000..4b398176
--- /dev/null
+++ b/packages/vite-plugin-checker/__tests__/unit/__snapshots__/logger.spec.ts.snap
@@ -0,0 +1,29 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`logger diagnosticToTerminalLog get error 1`] = `
+" ERROR(ESLint)  Unexpected var, use let or const instead.
+ FILE  /Users/vite-plugin-checker/playground/vanilla-ts/src/main.ts:3:1
+
+    1 | import { text } from './text'
+    2 |
+  > 3 | var hello = 'Hello'
+      | ^^^^^^^^^^^^^^^^^^^
+    4 |
+    5 | const rootDom = document.querySelector('#root')!
+    6 | rootDom.innerHTML = hello + text
+"
+`;
+
+exports[`logger diagnosticToTerminalLog get warning 1`] = `
+" WARNING(ESLint)  Unexpected var, use let or const instead.
+ FILE  /Users/vite-plugin-checker/playground/vanilla-ts/src/main.ts:3:1
+
+    1 | import { text } from './text'
+    2 |
+  > 3 | var hello = 'Hello'
+      | ^^^^^^^^^^^^^^^^^^^
+    4 |
+    5 | const rootDom = document.querySelector('#root')!
+    6 | rootDom.innerHTML = hello + text
+"
+`;
diff --git a/packages/vite-plugin-checker/__tests__/unit/fixtures/eslintDiagnostic.ts b/packages/vite-plugin-checker/__tests__/unit/fixtures/eslintDiagnostic.ts
new file mode 100644
index 00000000..92db2688
--- /dev/null
+++ b/packages/vite-plugin-checker/__tests__/unit/fixtures/eslintDiagnostic.ts
@@ -0,0 +1,14 @@
+export const error1 = {
+  message: 'Unexpected var, use let or const instead.',
+  conclusion: '',
+  codeFrame:
+    "  \u001b[0m \u001b[90m 1 |\u001b[39m \u001b[36mimport\u001b[39m { text } \u001b[36mfrom\u001b[39m \u001b[32m'./text'\u001b[39m\u001b[0m\n  \u001b[0m \u001b[90m 2 |\u001b[39m\u001b[0m\n  \u001b[0m\u001b[31m\u001b[1m>\u001b[22m\u001b[39m\u001b[90m 3 |\u001b[39m \u001b[36mvar\u001b[39m hello \u001b[33m=\u001b[39m \u001b[32m'Hello'\u001b[39m\u001b[0m\n  \u001b[0m \u001b[90m   |\u001b[39m \u001b[31m\u001b[1m^\u001b[22m\u001b[39m\u001b[31m\u001b[1m^\u001b[22m\u001b[39m\u001b[31m\u001b[1m^\u001b[22m\u001b[39m\u001b[31m\u001b[1m^\u001b[22m\u001b[39m\u001b[31m\u001b[1m^\u001b[22m\u001b[39m\u001b[31m\u001b[1m^\u001b[22m\u001b[39m\u001b[31m\u001b[1m^\u001b[22m\u001b[39m\u001b[31m\u001b[1m^\u001b[22m\u001b[39m\u001b[31m\u001b[1m^\u001b[22m\u001b[39m\u001b[31m\u001b[1m^\u001b[22m\u001b[39m\u001b[31m\u001b[1m^\u001b[22m\u001b[39m\u001b[31m\u001b[1m^\u001b[22m\u001b[39m\u001b[31m\u001b[1m^\u001b[22m\u001b[39m\u001b[31m\u001b[1m^\u001b[22m\u001b[39m\u001b[31m\u001b[1m^\u001b[22m\u001b[39m\u001b[31m\u001b[1m^\u001b[22m\u001b[39m\u001b[31m\u001b[1m^\u001b[22m\u001b[39m\u001b[31m\u001b[1m^\u001b[22m\u001b[39m\u001b[31m\u001b[1m^\u001b[22m\u001b[39m\u001b[0m\n  \u001b[0m \u001b[90m 4 |\u001b[39m\u001b[0m\n  \u001b[0m \u001b[90m 5 |\u001b[39m \u001b[36mconst\u001b[39m rootDom \u001b[33m=\u001b[39m document\u001b[33m.\u001b[39mquerySelector(\u001b[32m'#root'\u001b[39m)\u001b[33m!\u001b[39m\u001b[0m\n  \u001b[0m \u001b[90m 6 |\u001b[39m rootDom\u001b[33m.\u001b[39minnerHTML \u001b[33m=\u001b[39m hello \u001b[33m+\u001b[39m text\u001b[0m",
+  stripedCodeFrame:
+    "    1 | import { text } from './text'\n    2 |\n  > 3 | var hello = 'Hello'\n      | ^^^^^^^^^^^^^^^^^^^\n    4 |\n    5 | const rootDom = document.querySelector('#root')!\n    6 | rootDom.innerHTML = hello + text",
+  id: '/Users/vite-plugin-checker/playground/vanilla-ts/src/main.ts',
+  checker: 'ESLint',
+  loc: { start: { line: 3, column: 1 }, end: { line: 3, column: 20 } },
+  level: 1,
+} as const
+
+export const warning1 = { ...error1, level: 0 }
diff --git a/packages/vite-plugin-checker/__tests__/unit/logger.spec.ts b/packages/vite-plugin-checker/__tests__/unit/logger.spec.ts
new file mode 100644
index 00000000..6e574d8a
--- /dev/null
+++ b/packages/vite-plugin-checker/__tests__/unit/logger.spec.ts
@@ -0,0 +1,17 @@
+import { diagnosticToTerminalLog } from '../../src/logger'
+import { error1 as eslintError1, warning1 as eslintWarning1 } from './fixtures/eslintDiagnostic'
+import strip from 'strip-ansi'
+
+describe('logger', () => {
+  describe('diagnosticToTerminalLog', () => {
+    it('get error', () => {
+      const receive = strip(diagnosticToTerminalLog(eslintError1, 'ESLint'))
+      expect(receive).toMatchSnapshot()
+    })
+
+    it('get warning', () => {
+      const receive = strip(diagnosticToTerminalLog(eslintWarning1, 'ESLint'))
+      expect(receive).toMatchSnapshot()
+    })
+  })
+})
diff --git a/packages/vite-plugin-checker/src/logger.ts b/packages/vite-plugin-checker/src/logger.ts
index d50b85a2..2b0253df 100644
--- a/packages/vite-plugin-checker/src/logger.ts
+++ b/packages/vite-plugin-checker/src/logger.ts
@@ -65,7 +65,7 @@ export function diagnosticToTerminalLog(
     [DiagnosticLevel.Message]: boldBlack.bgCyanBright(` MESSAGE${nameInLabel} `),
   }
 
-  const levelLabel = labelMap[d.level || DiagnosticLevel.Error]
+  const levelLabel = labelMap[d.level ?? DiagnosticLevel.Error]
   const fileLabel = boldBlack.bgCyanBright(' FILE ') + ' '
   const position = d.loc
     ? chalk.yellow(d.loc.start.line) + ':' + chalk.yellow(d.loc.start.column)