diff --git a/src/compareCommits.ts b/src/compareCommits.ts
index 8895fdb..46edcee 100644
--- a/src/compareCommits.ts
+++ b/src/compareCommits.ts
@@ -1,17 +1,14 @@
 import {context} from '@actions/github'
 import {octokit} from './client'
 
-export class CommitsComparison {
-  constructor(public newFiles: string[], public modifiedFiles: string[]) {}
+export type CommitsComparison = {
+  newFiles: string[]
+  modifiedFiles: string[]
 }
 
 export async function compareCommits(base: string, head: string): Promise<CommitsComparison> {
-  const response = await octokit.rest.repos.compareCommits({
-    base,
-    head,
-    owner: context.repo.owner,
-    repo: context.repo.repo
-  })
+  const {owner, repo} = context.repo
+  const response = await octokit.rest.repos.compareCommits({base, head, owner, repo})
 
   const files = response.data.files ?? []
 
@@ -23,5 +20,5 @@ export async function compareCommits(base: string, head: string): Promise<Commit
     if (file.status === 'added') newFiles.push(file.filename)
     if (file.status === 'modified') modifiedFiles.push(file.filename)
   }
-  return new CommitsComparison(newFiles, modifiedFiles)
+  return {newFiles, modifiedFiles}
 }
diff --git a/src/index.ts b/src/index.ts
index 1da1eae..b94684e 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -4,8 +4,9 @@ import {parseCoverageReport} from './coverage'
 import {compareCommits} from './compareCommits'
 import {messagePr} from './messagePr'
 import {octokit} from './client'
+import readFile from './readFile'
 
-import * as fs from 'fs'
+const checkName = 'Coverge Results'
 
 async function run(): Promise<void> {
   try {
@@ -15,11 +16,12 @@ async function run(): Promise<void> {
     const eventName = context.eventName
     if (eventName !== 'pull_request') {
       core.setFailed(`action support only pull requests but event is ${eventName}`)
+      return;
     }
-    const base = context.payload.pull_request?.base.sha
-    const head = context.payload.pull_request?.head.sha
+    const {pull_request} = context.payload
+    const base = pull_request?.base.sha
+    const head = pull_request?.head.sha
 
-    const checkName = 'Coverge Results'
     const checks = await octokit.rest.checks.listForRef({
       ...context.repo,
       ref: head
@@ -52,7 +54,7 @@ async function run(): Promise<void> {
     const files = await compareCommits(base, head)
     core.info(`git new files: ${JSON.stringify(files.newFiles)} modified files: ${JSON.stringify(files.modifiedFiles)}`)
 
-    const report = fs.readFileSync(coverageFile, 'utf8')
+    const report = readFile(coverageFile)
     const filesCoverage = parseCoverageReport(report, files)
     const {passOverall, message} = messagePr(filesCoverage)
 
diff --git a/src/readFile.ts b/src/readFile.ts
new file mode 100644
index 0000000..ee4e31b
--- /dev/null
+++ b/src/readFile.ts
@@ -0,0 +1,11 @@
+import * as fs from 'fs'
+
+const readFile = (path: string): string => {
+  try {
+    return fs.readFileSync(path, 'utf8')
+  } catch (error) {
+    throw new Error(`could not read file ${path}`)
+  }
+}
+
+export default readFile