Call Test Class

 PageReference pageref = Page.ProcessSingleLeadInquiryIntegraton;
        Test.setCurrentPage(pageRef);
        Apexpages.currentPage().getParameters().put('id',integ.Id); 
        ApexPages.StandardController stdAct = new ApexPages.StandardController(integ);
        LeadInquiryIntegrationExt leadinquiry = new LeadInquiryIntegrationExt(stdAct);
        
        leadinquiry.proceedSingleLeadInquryIntegration();
        leadinquiry.proceedAllNewLeadInquryIntegrations();

Account Billing City is update we need to update Contact Mailing City

trigger AccountTrigger on Account (after update)
  {
// Set will avoid duplicates
// here adding the account id in set
     Set<Id> set_accountId = new Set<Id>();
System.debug('Set the Account Values are : ' + set_accountId); // here getting values as null in list,set and map

//List is for bulk update
     List<Contact> contactList = new List<Contact>();
System.debug('List the Account Values are : ' + contactList);

// Map is having the list of account id and the list of contacts
Map<Id,List<Contact>> mp_ListContact = new Map<Id,List<Contact>>();
System.debug('Map the Account Values are : ' + mp_ListContact);

// Inside for loop we are adding the account id in the Set. Set will avoid duplicates
for(Account acc : Trigger.new)
  {
if(acc.billingcity!=Trigger.oldMap.get(acc.id).billingcity)
set_accountId.add(acc.id);
System.debug('Set the Account Values are : ' + set_accountId);
  }
 
  // In this for loop we are querying 'Contact' which is having the account.
  // Here we need to check the governor limits . Important about query : accountId IN : set_accountId
for(Contact con : [Select Id,AccountId,mailingcity from Contact where accountId IN : set_accountId limit 50000])
  {
// Adding the key and values
// Key is accountId
// Value is conlist
// conlist is having the accountid
//
if(mp_ListContact!=null && mp_ListContact.containsKey(con.AccountId))
{
List<Contact> conList = mp_ListContact.get(con.AccountId);
conList.add(con);
mp_ListContact.put(con.AccountId, conList);
}

else
mp_ListContact.put(con.AccountId, new List<Contact>{con});

   }


for(Account acc : Trigger.new)
  {
if(mp_ListContact!=null && mp_ListContact.containsKey(acc.id))
{
for(Contact con : mp_ListContact.get(acc.id))
{
  // Write logic to update contact as sample below :
  con.mailingcity= acc.billingcity;
  con.FirstName = acc.Name;
  contactList.add(con);
  }
}
   }

if(contactList!=null && contactList.size()>0){
update contactList;
}
 

}

Count Account having Contacts : using group by

Select count(name) from Contact group by AccountId

Output:

When we use @isTest(seeAllData = true) ?

In salesforce, we have 2 types of object
  Setup objects are like : (Where we can Create)

  Profile

  Record Type,

  Users

Non Setup Objetcs are like :

Contact

Lead

Account

Non-Setup objects are standard objects like Account or any custom object.

Setup objects are Group1, GroupMember, QueueSObject, User2, UserRole, UserTerritory, Territory, etc.

We cannot create a test data for non-setup objects. That time we need use in our test class as "@isTest(seeAllData = true)"

Count Number of Attachements in object

trigger countattachment on Attachment (after insert, after update, after delete, after undelete) {
  Map<Id,List<Attachment>> parent = new Map<Id,List<Attachment>>();
  set<id> attids = new set<id>();
     
   if(Trigger.new<>null){
       for(Attachment c:Trigger.new){
           TestObject__c l;
           if(c.ParentId != null)
               attids.add(c.parentid);
       }
           
   }else if(Trigger.old != null){
       for(Attachment c:Trigger.old){
           if(c.ParentId<>null)      
               attids.add(Trigger.oldMap.get(c.id).parentid);
       }
   }
   if(attids.size()>0){
       try{
           List<Attachment> a = new List<Attachment>();
           Map<id,TestObject__c> testmap = new Map<id,TestObject__c>([select id,CountAttachment__c from TestObject__c where id IN: attids]);
           a = [select id,parentid from Attachment where parentid IN:attids];
           
           for(Attachment at: a){
               List<Attachment> llist = new List<Attachment>();
               if(parent.get(at.parentid) == null){
                   llist = new List<Attachment>();
                   llist.add(at);
                   parent.put(at.parentid,llist);
               }else if(parent.get(at.parentid) != null){
                   llist = new List<Attachment>();
                   llist = parent.get(at.parentid);
                   llist.add(at);
                   parent.put(at.parentid,llist);
               }
           }
           
           for(Id i: attids){
               if(testmap.get(i) != null && parent.get(i) != null){
                  testmap.get(i).CountAttachment__c = parent.get(i).size(); 
               
               }else if(testmap.get(i) != null && parent.get(i) == null){
                  testmap.get(i).CountAttachment__c = 0; 
               }
           }
       
           update testmap.values();
           System.Debug(testmap.values());
       }catch(Exception e){}
    }

}

System Mode vs User Mode in salesforce.

User Mode - Profile level permissions, field-level security, and sharing rules of the current user are enforced.

System Mode - Object permissions, field-level security, sharing rules aren't applied for the current user.

This is the consolidated list of execution and mode of execution:

• Trigger - System
• Validation Rule - System
• Auto Response Rule - System
• Assignment Rule - System
• Workflow Rule - System
• Escalation Rule - System
• All Types of calculation behind formula, Rollup Summary - System
• Process Builder - System
• Visual Workflow or flow - User
  • if flow is called from Process Builder - System
  • if flow is called from Workflow - System
  • if flow is called from Apex - (depends on with or w/o sharing of apex class)
  • if flow is called from Custom Button - System
  • if flow is embed in Visualforce - Depends on VFP context
  • if flow is called from REST API - System
• Approval Process - System
• Publisher Action - System
• InvocableMethod
  • if this is called from flow - User
  • if this is called from Process Builder (does it depends on with or without sharing is specified on that Class) - System
  • if this is called from REST API - (depends on with or w/o sharing of the class)
• Custom Button - System
• Test method with System.runAs() - User
• Test method without System.runAs() - System
• Visualforce Page (StandardController) - User
• Visualforce Page (StandardController with extension) - System
• Visualforce Page (Custom Controller)
  • depends on with or without sharing of the controller
• Visualforce Component - depends on Visualforce page where it is used
• Macros - System
• Annonymous Apex - User
• Chatter in Apex - User
• Email Service - User
• Batch Class  - User
• All types of Jobs - System
• Apex Webservices (SOAP API and REST API) - System (Consequently, the current user's credentials are not used, and any user who has access to these methods can use their full power, regardless of permissions, field-level security, or sharing rules.)