How can we implement a test class on map in Salesforce apex?

Hello Anurag,

You can refer the following example to implement a test class of Map:

Apex Class:

public class Task14 {

public static void beforeupdate(Map<id,Account> oldmap,Map<id,Account> newmap){
list<id> accid=new list<id>();
for(id key:oldmap.keySet()){
Account old=oldmap.get(key);
Account newmp=newmap.get(key);
if(old.Phone!=newmp.Phone){
accid.add(key);
}
}
list<Contact> con=[select lastname,firstname,phone,accountid from Contact where accountid in:accid];
for(Contact c:con){
Account a=newmap.get(c.accountid);
Account b=oldmap.get(c.accountid);
c.Phone=a.Phone;
c.OtherPhone=b.phone;

}
update con;
}
}
Trigger:

trigger Task14Trigger on Account (before update) {
if(trigger.isbefore && trigger.isupdate){
Task14.beforeupdate(Trigger.oldmap, Trigger.newmap);
}
}

Test Class:

@isTest
private class Task14_Test {

@isTest static void beforeupdateTest() {
Map<id,Account> oldmap = new Map<id,Account>();
Map<id,Account> newmap = new Map<id,Account>();
Account acct = new Account(Name='Test Account',phone='123456789');
insert acct;
oldmap.put(acct.id, acct);

contact con = new contact();
con.accountid = acct.id;
con.LastName = 'TestContact';
insert con;

// Perform test
Test.startTest();
acct.Phone = '987654321';
update acct;
newmap.put(acct.id, acct);

Task14.beforeupdate(oldmap,newmap);
Test.stopTest();

system.assertEquals('987654321', acct.Phone);
}

}

Thanks.