Hi I don't post code before, and thought that's lazy and waste other one's time.

But I really don't get it, it works very well in Sandbox, but testClass doesn't give green light.

1. What I have made. 

• There is one look up field link to User on Contact page, the contact is staff of our Org.
• There have 2 trigger which update the Phone number for both sides

       Such as when Admin update the phone number on Staff page, trigger update it to User's profile, and opposite way.

2. I finished the 2 trigger, and then write the testClass.

    I tried a lot, but it doesn't work, then I try to test it with real data in sandbox, nothing wrong, even Chatter Free User could work with these triggers. 

3. Then I try to comment the System.Assert part, I could still get 100 % cover, but I don't feel that's the correct way I should do.

     I also reviewed my code a lot, I still can't find how to make the testClass correct. 

Trigger 1

trigger ChattterToStaff on User (after update) {
	
	for(User SFUser: trigger.new)
	{
		User oldSFUser = Trigger.oldMap.get(SFUser.Id);
		List<Contact> staff = new List<Contact>();
		staff = [SELECT Id from Contact Where User__c=:SFUser.Id];
		
		If(staff.size()==1)
		{
			If(oldSFUser.Phone != SFUser.Phone)
			{
				staff[0].Phone = SFUser.Phone;
				update staff;
			}
			If(oldSFUser.MobilePhone != SFUser.MobilePhone)
			{
				staff[0].MobilePhone = SFUser.MobilePhone;
				update staff;
			}		
		}
	}
}

Trigger 2

trigger StaffToChatter on Contact (after update) {
	
	for(Contact Staff : trigger.new)
	{
		If(Staff.User__c !=null)
		{
			Contact oldStaff = Trigger.oldMap.get(Staff.Id);
			User SFUser = new User();
			SFUser.Id = Staff.User__c;
			If(oldStaff.Phone != Staff.Phone)
			{
				SFUser.Phone = Staff.Phone;
				update SFUser;
			}
			If(oldStaff.MobilePhone != Staff.MobilePhone)
			{
				SFUser.MobilePhone = Staff.MobilePhone;
				update SFUser;
			}
		}
	}
}

TestClass

@isTest
private class testChatterWithStaff {

    static testMethod void myUnitTest() {
        Profile pf = [select Id from Profile where Name='Standard User'];
        User testUser1 = new User(
        alias = 'test1', 
        email='test1@noemail.com',
        emailencodingkey='UTF-8', 
        lastname='Testing', 
        languagelocalekey='en_US',
        localesidkey='en_US', 
        profileid = pf.Id, 
        country='United States',
        timezonesidkey='America/Los_Angeles', 
        username='test1@noemail.com');
        insert testUser1;
        
        Id StaffRecordTypeId = Schema.SObjectType.Contact.getRecordTypeInfosByName().get('Staff').getRecordTypeId();
        //initial test Contact
        Contact testContact = new contact(FirstName='test', LastName='Test', RecordTypeId = StaffRecordTypeId);
        insert testContact;
        testContact.User__c = testUser1.Id;
        update testContact;
        System.Debug('User is '+testContact.User__c);//correct
        
        testContact.Phone = '212-975-4321';
        update testContact;
        System.Debug('testContact Phone is'+testContact.Phone);
        System.Debug('testUser1 Phone is ' +testUser1.Phone); //User is not updated.
        System.assertEquals(testContact.Phone , testUser1.Phone);
        testContact.MobilePhone = ' 604-684-7221';
        update testContact;
        System.assertEquals(testContact.MobilePHone , testUser1.MobilePhone);  
        
        testUser1.Phone = '202-456-1121';
        update testUser1;
        System.assertEquals(testUser1.Phone , testContact.Phone);
        testUser1.MobilePhone = '202-456-9713';
        update testUser1;
        System.assertEquals(testUser1.MobilePhone , testContact.MobilePhone);   

    }
}