Can anyone provide Test class for following scenario.Consider all positive negative Bulk testing for the given batch class.
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Use Case ::
Removal of duplicate Leads
1. During the Campaigning, It might happen that representative creates duplicate leads in an org.
2. So admin want to build a process which will run every 3 hours/day & remove the duplicate leads from the org.
3. The criteria to find the duplicate records should be configurable. Ex. If there are two leads in a system with same Email address then keep the first lead entry & remove all the other leads. So the field like Email, Name which will be deciding the uniqueness should be configurable.


--------------------------------------------------BATCH class----------------------------------------------
global class RemoveDuplicateLeads implements Database.Batchable<sObject>, Database.Stateful {
/**
Map will Keep count of Lead which are having same field
*/
Map<String,Integer> countMap = new Map<String,Integer>();
/**
Constructor to initialize the countMap. Which will be useful for every batch operation.
*/
global RemoveDuplicateLeads() {
Database.QueryLocatorIterator iterator =
Database.getQueryLocator('select ' + System.Label.Lead_Field + ' from Lead').iterator();
while (iterator.hasNext())
{
Lead leadRecord = (Lead) iterator.next();
if(leadRecord.get(System.Label.Lead_Field) != null) {
countMap.put((String)leadRecord.get(System.Label.Lead_Field), 0);
}
}
}

/**
This method will start the batch execution.
@return Database.QueryLocator - This will contain all Leads.
*/
global Database.QueryLocator start(Database.BatchableContext BC) {
return Database.getQueryLocator('select ' + System.Label.Lead_Field + ' from lead');
}

/**
This method will execute for every batch and deletes the duplicate leads.
@return Nothing.
*/
global void execute(Database.BatchableContext BC, List<sObject> scope) {
List<Lead> leadList = new List<Lead>();
for(SObject lead : scope) {
if(lead.get(System.Label.Lead_Field) != null) {
if(countMap.get((String)lead.get(System.Label.Lead_Field)) >= 1 ) {
leadList.add((Lead)lead);
} else {
countMap.put((String)lead.get(System.Label.Lead_Field),1);
}
}
}
Database.delete(leadList,false);
}
/**
This method will execute at end of Batch apex process.
@return Nothing.
*/
global void finish(Database.BatchableContext BC) {
}
}