Following the AccountSearchController

AccountSearchControllerTest

@isTest
public with sharing class AccountSearchControllerTest {

    @isTest
    public static void testAccountSearchController() {
            Account acct = new Account(Name ='Test ');
            acct.BillingPostalCode = '106-0044';
            acct.BillingCountry = 'JP';
            acct.BillingState = '東京都';
            acct.BillingCity = '港区';
            acct.BillingStreet = '芝公園3-1-1';
            acct.BillingLatitude = 35.661;
            acct.BillingLongitude = 139.748;
        insert acct;
        
        List<Lead> leads = new List<Lead>();
            Lead lead = new Lead (LastName ='Test ');
            lead.PostalCode = '106-0044';
            lead.Country = 'JP';
            lead.State = '東京都';
            lead.City = '港区';
            lead.Street = '芝公園3-1-1';
            lead.Latitude = 35.661;
            lead.Longitude = 139.748; 
        insert lead;
        
   Test.startTest();
        
        Id [] fixedSearchResults= new Id[1];
        fixedSearchResults[0] = acct.Id;
        Test.setFixedSearchResults(fixedSearchResults);
        List<Account> searchAccounts = AccountSearchController.searchAccounts(acct.BillingState,'option1',25,6);
        System.assertEquals(false,searchAccounts.isEmpty());

        Id [] fixedSearchResults1= new Id[1];
        fixedSearchResults1[0] = acct.Id;
        Test.setFixedSearchResults(fixedSearchResults1);        
        List<Account> searchAccounts1 = AccountSearchController.searchAccounts(null,'option1',25,6);
        System.assertEquals('東京都',searchAccounts1[0].BillingState);
        
        Id [] fixedSearchResults2= new Id[1];
        fixedSearchResults2[0] = lead.Id;
        Test.setFixedSearchResults(fixedSearchResults2);
        List<Lead> searchLeads = AccountSearchController.searchLeads('東京都','option2',25,6);
        System.assertEquals(false,searchLeads.isEmpty());
        
        Id [] fixedSearchResults4= new Id[1];
        fixedSearchResults4[0] = lead.Id;
        Test.setFixedSearchResults(fixedSearchResults4);
        List<Lead> searchLeads1 = AccountSearchController.searchLeads(null,'option2',25,6);
        System.assertEquals('東京都',searchLeads1[0].State);
        
        Test.stopTest();

    }
}