My test class is failing stating that "Methods defined as TestMethod do not support Web service callouts". Please find my classes below:-

@RestResource(urlMapping='/Accounts/*/contacts')
global class AccountManager {
    @HttpGet
    global static Account getAccount() {
        RestRequest req = RestContext.request;
        String accId = req.requestURI.substringBetween('Accounts/', '/contacts');
        Account acc = [SELECT Id, Name, (SELECT Id, Name FROM contacts) 
                       FROM Account WHERE Id = :accId];
        return acc;
    }
}




@isTest
private class AccountManagerTest {
@isTest
    private static  void testGetAccount(){
        Id recordId = createTestRecord();
        RestRequest request = new RestRequest();
        request.requestUri = 'https://sumankumari360-dev-ed.my.salesforce.com/services/apexrest/Accounts/'+recordId+'/contacts';
        request.httpMethod = 'GET';
        RestContext.request = request;
        Account thisAccount = AccountManager.getAccount();
        System.assert(thisAccount != null);
        System.assertEquals('Test record', thisAccount.Name);
    }
    static Id createTestRecord(){
         Account TestAcc = new Account(
          Name='Test record');
        insert TestAcc;
        Contact TestCon= new Contact(
        LastName='Test', 
        AccountId = TestAcc.id);
        return TestAcc.Id;
    }      
}
    
}