diff --git a/frontend/types/user.ts b/frontend/types/user.ts
index 2ca3727..39b1368 100644
--- a/frontend/types/user.ts
+++ b/frontend/types/user.ts
@@ -6,7 +6,7 @@ export type UserType = {
   password: string;
   username: string;
   role: number;
-  avatarPath: string;
+  avatarPath: string | null;
 } | null;
 
 export type TokenProps = {
diff --git a/frontend/utils/TokenProvider.tsx b/frontend/utils/TokenProvider.tsx
index 7892007..100b5f9 100644
--- a/frontend/utils/TokenProvider.tsx
+++ b/frontend/utils/TokenProvider.tsx
@@ -3,7 +3,11 @@ import { createContext, useState, useEffect, useContext } from 'react';
 import { TokenContextType, TokenType } from '@/types/user';
 import { TokenProps } from '@/types/user';
 import { useRouter, usePathname } from '@/src/navigation';
-import { roles } from '@/config/selection';
+import {
+  isSignedIn as tokenIsSinedIn,
+  isAdmin as tokenIsAdmin,
+  checkSignInPage as tokenCheckSignInPage,
+} from './token';
 import { ToastContext } from './ToastProvider';
 const LOCAL_STORAGE_KEY = 'testplat-auth-token';
 
@@ -40,39 +44,12 @@ const TokenProvider = ({ toastMessages, locale, children }: TokenProps) => {
     user: null,
   });
 
-  const tokenExists = () => {
-    if (token && token.user && token.user.username) {
-      return true;
-    } else {
-      return false;
-    }
-  };
-
-  const isTokenValid = () => {
-    if (Date.now() < token.expires_at) {
-      return true;
-    } else {
-      return false;
-    }
-  };
-
   const isSignedIn = () => {
-    if (tokenExists() && isTokenValid()) {
-      return true;
-    } else {
-      return false;
-    }
+    return tokenIsSinedIn(token);
   };
 
   const isAdmin = () => {
-    if (tokenExists() && isTokenValid()) {
-      const adminRoleIndex = roles.findIndex((entry) => entry.uid === 'administrator');
-      if (token.user.role === adminRoleIndex) {
-        return true;
-      }
-    } else {
-      return false;
-    }
+    return tokenIsAdmin(token);
   };
 
   const tokenContext = {
@@ -98,32 +75,7 @@ const TokenProvider = ({ toastMessages, locale, children }: TokenProps) => {
   }, []);
 
   useEffect(() => {
-    // pravate paths are '/account', '/admin', '/projects/*'
-    const isPrivatePath = (pathname: string) => {
-      return (
-        /^\/account(\/)?$/.test(pathname) || /^\/admin(\/)?$/.test(pathname) || /^\/projects(\/.*)?$/.test(pathname)
-      );
-    };
-
-    const checkSignInPage = () => {
-      if (!hasRestoreFinished) {
-        return;
-      }
-      if (isPrivatePath(pathname) && !isSignedIn()) {
-        if (tokenExists()) {
-          toastContext.showToast(toastMessages.needSignedIn, 'error');
-          router.push(`/account/signin`, { locale: locale });
-          return;
-        }
-        if (isTokenValid()) {
-          toastContext.showToast(toastMessages.sessionExpired, 'error');
-          router.push(`/account/signin`, { locale: locale });
-          return;
-        }
-      }
-    };
-
-    checkSignInPage();
+    tokenCheckSignInPage(token, pathname);
   }, [pathname, hasRestoreFinished]);
 
   return <TokenContext.Provider value={tokenContext}>{children}</TokenContext.Provider>;
diff --git a/frontend/utils/token.test.ts b/frontend/utils/token.test.ts
new file mode 100644
index 0000000..324b0a0
--- /dev/null
+++ b/frontend/utils/token.test.ts
@@ -0,0 +1,137 @@
+import { describe, expect, test } from 'vitest';
+import { isPrivatePath, checkSignInPage, isAdmin } from './token';
+
+describe('check account path', () => {
+  test('"account/" is private', () => {
+    expect(isPrivatePath('/account')).toBe(true);
+  });
+  test('"account/signin" is public', () => {
+    expect(isPrivatePath('/account/signin')).toBe(false);
+  });
+  test('"account/signup" is public', () => {
+    expect(isPrivatePath('/account/signup')).toBe(false);
+  });
+});
+
+describe('check admin path', () => {
+  test('"admin/" is private', () => {
+    expect(isPrivatePath('/admin')).toBe(true);
+  });
+  test('"admin/something" is private', () => {
+    expect(isPrivatePath('/admin/signin')).toBe(true);
+  });
+});
+
+describe('check projects path', () => {
+  test('"projects/" is private', () => {
+    expect(isPrivatePath('/projects')).toBe(true);
+  });
+  test('"projects/1" is private', () => {
+    expect(isPrivatePath('/projects/1')).toBe(true);
+  });
+});
+
+const validAdminToken = {
+  access_token: 'loremipsumdolorsitametconsecteturadipiscingelit',
+  expires_at: Infinity,
+  user: {
+    id: 1,
+    email: 'admin@example.com',
+    password: 'hashedpassword',
+    username: 'admin',
+    role: 0,
+    avatarPath: null,
+    createdAt: '2024-06-01T00:18:03.859Z',
+    updatedAt: '2024-06-01T00:18:03.859Z',
+  },
+};
+
+const validUserToken = {
+  access_token: 'loremipsumdolorsitametconsecteturadipiscingelit',
+  expires_at: Infinity,
+  user: {
+    id: 2,
+    email: 'user@example.com',
+    password: 'hashedpassword',
+    username: 'user',
+    role: 1,
+    avatarPath: null,
+    createdAt: '2024-06-01T00:18:03.859Z',
+    updatedAt: '2024-06-01T00:18:03.859Z',
+  },
+};
+
+const expiredUserToken = {
+  access_token: 'loremipsumdolorsitametconsecteturadipiscingelit',
+  expires_at: 1717200000000,
+  user: {
+    id: 2,
+    email: 'user@example.com',
+    password: 'hashedpassword',
+    username: 'user',
+    role: 1,
+    avatarPath: null,
+    createdAt: '2024-06-01T00:18:03.859Z',
+    updatedAt: '2024-06-01T00:18:03.859Z',
+  },
+};
+
+describe('check user is admin or not', () => {
+  test('user with admin role is admin', () => {
+    expect(isAdmin(validAdminToken)).toBe(true);
+  });
+
+  test('user with user role is not admin', () => {
+    expect(isAdmin(validUserToken)).toBe(false);
+  });
+});
+
+describe('check sign in', () => {
+  test('Access to public paths by not signed user will be allowed', () => {
+    const token = {
+      access_token: '',
+      expires_at: 0,
+      user: null,
+    };
+
+    const privatePath = '/';
+    expect(checkSignInPage(token, privatePath)).toStrictEqual({
+      ok: true,
+      reason: '',
+      redirectPath: '',
+    });
+  });
+
+  test('Access to private paths by not signed user in will be redirected', () => {
+    const token = {
+      access_token: '',
+      expires_at: 0,
+      user: null,
+    };
+
+    const privatePath = '/account';
+    expect(checkSignInPage(token, privatePath)).toStrictEqual({
+      ok: false,
+      reason: 'notoken',
+      redirectPath: '/account/signin',
+    });
+  });
+
+  test('Access to private paths by signed in user will be allowed', () => {
+    const privatePath = '/account';
+    expect(checkSignInPage(validAdminToken, privatePath)).toStrictEqual({
+      ok: true,
+      reason: '',
+      redirectPath: '',
+    });
+  });
+
+  test('Access to private paths by user whose token expired will be redirected', () => {
+    const privatePath = '/account';
+    expect(checkSignInPage(expiredUserToken, privatePath)).toStrictEqual({
+      ok: false,
+      reason: 'expired',
+      redirectPath: '/account/signin',
+    });
+  });
+});
diff --git a/frontend/utils/token.ts b/frontend/utils/token.ts
new file mode 100644
index 0000000..5edab7a
--- /dev/null
+++ b/frontend/utils/token.ts
@@ -0,0 +1,69 @@
+import { TokenType } from '@/types/user';
+import { roles } from '@/config/selection';
+
+function tokenExists(token: TokenType) {
+  if (token && token.user && token.user.username) {
+    return true;
+  } else {
+    return false;
+  }
+}
+
+function isTokenValid(token: TokenType) {
+  if (Date.now() < token.expires_at) {
+    return true;
+  } else {
+    return false;
+  }
+}
+
+function isSignedIn(token: TokenType): boolean {
+  if (tokenExists(token) && isTokenValid(token)) {
+    return true;
+  } else {
+    return false;
+  }
+}
+
+function isAdmin(token: TokenType) {
+  if (tokenExists(token) && isTokenValid(token)) {
+    const adminRoleIndex = roles.findIndex((entry) => entry.uid === 'administrator');
+    if (token.user.role === adminRoleIndex) {
+      return true;
+    }
+  }
+
+  return false;
+}
+
+// pravate paths are '/account', '/admin', '/projects/*'
+const isPrivatePath = (pathname: string) => {
+  return /^\/account(\/)?$/.test(pathname) || /^\/admin(\/.*)?$/.test(pathname) || /^\/projects(\/.*)?$/.test(pathname);
+};
+
+function checkSignInPage(token: TokenType, pathname: string) {
+  let ret = {
+    ok: true,
+    reason: '',
+    redirectPath: '',
+  };
+
+  if (isPrivatePath(pathname) && !isSignedIn(token)) {
+    if (!tokenExists(token)) {
+      ret.ok = false;
+      ret.reason = 'notoken';
+      ret.redirectPath = '/account/signin';
+      return ret;
+    }
+    if (!isTokenValid(token)) {
+      ret.ok = false;
+      ret.reason = 'expired';
+      ret.redirectPath = '/account/signin';
+      return ret;
+    }
+  }
+
+  return ret;
+}
+
+export { isSignedIn, isAdmin, isPrivatePath, checkSignInPage };
diff --git a/vitest.config.ts b/vitest.config.ts
index 50a0ce7..6143f1e 100644
--- a/vitest.config.ts
+++ b/vitest.config.ts
@@ -1,10 +1,14 @@
-import { defineConfig } from "vitest/config";
+import { defineConfig } from 'vitest/config';
+import { resolve } from 'node:path';
 
 export default defineConfig({
   test: {
     coverage: {
       exclude: ['**/node_modules/**', 'docs/**', '**/.next/**'],
-      provider: "v8",
+      provider: 'v8',
     },
   },
+  resolve: {
+    alias: [{ find: '@', replacement: resolve(__dirname, './frontend') }],
+  },
 });