diff --git a/__tests__/git-utils.test.ts b/__tests__/git-utils.test.ts
new file mode 100644
index 0000000..d8b94c4
--- /dev/null
+++ b/__tests__/git-utils.test.ts
@@ -0,0 +1,116 @@
+import {getUserName, getUserEmail, setCommitAuthor} from '../src/git-utils';
+import {getWorkDirName, createWorkDir} from '../src/utils';
+import {CmdResult} from '../src/interfaces';
+import * as exec from '@actions/exec';
+
+beforeEach(() => {
+  jest.resetModules();
+  process.env['GITHUB_ACTOR'] = 'default-octocat';
+  process.env['GITHUB_REPOSITORY'] = 'owner/repo';
+});
+
+afterEach(() => {
+  delete process.env['GITHUB_ACTOR'];
+  delete process.env['GITHUB_REPOSITORY'];
+});
+
+describe('getUserName()', () => {
+  test('get default git user name', () => {
+    const userName = '';
+    const test = getUserName(userName);
+    expect(test).toMatch('default-octocat');
+  });
+
+  test('get custom git user name', () => {
+    const userName = 'custom-octocat';
+    const test = getUserName(userName);
+    expect(test).toMatch(userName);
+  });
+});
+
+describe('getUserEmail()', () => {
+  test('get default git user email', () => {
+    const userEmail = '';
+    const test = getUserEmail(userEmail);
+    expect(test).toMatch('default-octocat@users.noreply.github.com');
+  });
+
+  test('get custom git user email', () => {
+    const userEmail = 'custom-octocat@github.com';
+    const test = getUserEmail(userEmail);
+    expect(test).toMatch(userEmail);
+  });
+});
+
+describe('setCommitAuthor()', () => {
+  let workDirName = '';
+  (async (): Promise<void> => {
+    const date = new Date();
+    const unixTime = date.getTime();
+    workDirName = await getWorkDirName(`${unixTime}`);
+  })();
+
+  beforeEach(async () => {
+    await createWorkDir(workDirName);
+    process.chdir(workDirName);
+    await exec.exec('git', ['init']);
+  });
+
+  test('get default commit author', async () => {
+    const userName = '';
+    const userEmail = '';
+    const result: CmdResult = {
+      exitcode: 0,
+      output: ''
+    };
+    const options = {
+      listeners: {
+        stdout: (data: Buffer): void => {
+          result.output += data.toString();
+        }
+      }
+    };
+    await setCommitAuthor(userName, userEmail);
+    result.exitcode = await exec.exec('git', ['config', 'user.name'], options);
+    expect(result.output).toMatch('default-octocat');
+    result.exitcode = await exec.exec('git', ['config', 'user.email'], options);
+    expect(result.output).toMatch('default-octocat@users.noreply.github.com');
+  });
+
+  test('get custom commit author', async () => {
+    const userName = 'custom-octocat';
+    const userEmail = 'custom-octocat@github.com';
+    const result: CmdResult = {
+      exitcode: 0,
+      output: ''
+    };
+    const options = {
+      listeners: {
+        stdout: (data: Buffer): void => {
+          result.output += data.toString();
+        }
+      }
+    };
+    await setCommitAuthor(userName, userEmail);
+    result.exitcode = await exec.exec('git', ['config', 'user.name'], options);
+    expect(result.output).toMatch(userName);
+    result.exitcode = await exec.exec('git', ['config', 'user.email'], options);
+    expect(result.output).toMatch(userEmail);
+  });
+
+  test('throw error user_email is undefined', async () => {
+    const userName = 'custom-octocat';
+    const userEmail = '';
+    await expect(setCommitAuthor(userName, userEmail)).rejects.toThrowError(
+      'user_email is undefined'
+    );
+  });
+
+  test('throw error user_name is undefined', async () => {
+    const userName = '';
+    const userEmail = 'custom-octocat@github.com';
+    await expect(setCommitAuthor(userName, userEmail)).rejects.toThrowError(
+      'user_name is undefined'
+    );
+  });
+});
diff --git a/src/git-utils.ts b/src/git-utils.ts
index cf291ef..8037be9 100644
--- a/src/git-utils.ts
+++ b/src/git-utils.ts
@@ -103,29 +103,34 @@ export async function setRepo(
   }
 }
 
-export async function setConfig(
+export function getUserName(userName: string): string {
+  if (userName) {
+    return userName;
+  } else {
+    return `${process.env.GITHUB_ACTOR}`;
+  }
+}
+
+export function getUserEmail(userEmail: string): string {
+  if (userEmail) {
+    return userEmail;
+  } else {
+    return `${process.env.GITHUB_ACTOR}@users.noreply.github.com`;
+  }
+}
+
+export async function setCommitAuthor(
   userName: string,
   userEmail: string
 ): Promise<void> {
-  await exec.exec('git', ['config', '--global', 'gc.auto', '0']);
-
-  let name = '';
-  if (userName) {
-    name = userName;
-  } else {
-    name = `${process.env.GITHUB_ACTOR}`;
+  if (userName && !userEmail) {
+    throw new Error('user_email is undefined');
   }
-  await exec.exec('git', ['config', '--global', 'user.name', name]);
-
-  let email = '';
-  if (userName !== '' && userEmail !== '') {
-    email = userEmail;
-  } else {
-    email = `${process.env.GITHUB_ACTOR}@users.noreply.github.com`;
+  if (!userName && userEmail) {
+    throw new Error('user_name is undefined');
   }
-  await exec.exec('git', ['config', '--global', 'user.email', email]);
-
-  return;
+  await exec.exec('git', ['config', 'user.name', getUserName(userName)]);
+  await exec.exec('git', ['config', 'user.email', getUserEmail(userEmail)]);
 }
 
 export async function commit(
diff --git a/src/main.ts b/src/main.ts
index 876cccf..2b47eef 100644
--- a/src/main.ts
+++ b/src/main.ts
@@ -3,7 +3,7 @@ import * as exec from '@actions/exec';
 import {Inputs} from './interfaces';
 import {showInputs, getInputs} from './get-inputs';
 import {setTokens} from './set-tokens';
-import * as git from './git-utils';
+import {setRepo, setCommitAuthor, commit, push, pushTag} from './git-utils';
 import {getWorkDirName, addNoJekyll, addCNAME} from './utils';
 
 export async function run(): Promise<void> {
@@ -11,15 +11,13 @@ export async function run(): Promise<void> {
     const inps: Inputs = getInputs();
     showInputs(inps);
 
-    await git.setConfig(inps.UserName, inps.UserEmail);
-
     const remoteURL = await setTokens(inps);
     core.debug(`[INFO] remoteURL: ${remoteURL}`);
 
     const date = new Date();
     const unixTime = date.getTime();
     const workDir = await getWorkDirName(`${unixTime}`);
-    await git.setRepo(inps, remoteURL, workDir);
+    await setRepo(inps, remoteURL, workDir);
 
     await addNoJekyll(workDir, inps.DisableNoJekyll, inps.PublishBranch);
     await addCNAME(workDir, inps.CNAME);
@@ -31,14 +29,14 @@ export async function run(): Promise<void> {
     }
     await exec.exec('git', ['remote', 'add', 'origin', remoteURL]);
     await exec.exec('git', ['add', '--all']);
-
-    await git.commit(
+    await setCommitAuthor(inps.UserName, inps.UserEmail);
+    await commit(
       inps.AllowEmptyCommit,
       inps.ExternalRepository,
       inps.CommitMessage
     );
-    await git.push(inps.PublishBranch, inps.ForceOrphan);
-    await git.pushTag(inps.TagName, inps.TagMessage);
+    await push(inps.PublishBranch, inps.ForceOrphan);
+    await pushTag(inps.TagName, inps.TagMessage);
 
     core.info('[INFO] Action successfully completed');