Hi,
Getting 50% code coverage.

Main class


@RestResource(urlMapping='/leadactivity/getlist/*')
global with sharing  class myActivityTask {
    
    @HttpGet
    global static  list<cust_map> doGetLead(){
        
        list<task> activityLog=new list<task> ();
        
        RestRequest req = RestContext.request;
        RestResponse res = RestContext.response;
        map<string,string> paramsMap=RestContext.request.params;
        string actdate=paramsMap.get('actdate');
        Datetime dt1 = Datetime.valueOf(actdate);
        list<cust_map> results = new list<cust_map>();        
        list<Task> taskList=[SELECT WhoId,CompletedDateTime,Id,who.type FROM Task where CreatedDate>:dt1];
        for(task str:taskList){
            cust_map obj = new cust_map();
            if(str.who.type!='Lead')
                continue;
           
            Lead result = [SELECT id FROM Lead WHERE Id = :str.WhoId];

            obj.LeadID =     str.WhoId;
         
            obj.CallDateTime = str.CompletedDateTime;
         
            results.add(obj);
        }
       
        return results;
    }
    global class cust_map{
        Global String LeadID=null;
        Global String CallCenterAgent=null;
        Global Datetime CallDateTime=null;
        Global String LMSID = null;
    }
    }
    

Test Class
=====
@isTest
private class MyActivityTask_Test{
   
   public testmethod static void MyActivityTask(){
       
       // insert lead data
       lead l = new lead();
       l.LastName = 'Test Lead';
       l.Company = 'Test Company';
       l.Status = 'Closed - Converted';
       insert l;
       
       task t = new task();
       t.Subject = 'Test Subject';
       t.Status = 'new';
       t.Priority = 'Normal';
       t.CallType = 'Outbound';
       t.WhoId = l.Id;
       insert t;
       
   system.Test.startTest();
       
       // call custom controller
       myActivityTask mat = new myActivityTask();
       myActivityTask.cust_map wrap = new myActivityTask.cust_map();
       wrap.LeadID = t.WhoId;
       wrap.CallDateTime = t.CompletedDateTime;
     
       RestResponse res = new RestResponse();
       RestRequest req = new RestRequest();
       
       req.params.put('actdate', 'my_actdate');
       
       req.httpMethod = 'Get';
       req.addHeader('Content-Type', 'application/json'); // Add a JSON Header as it is validated
       req.requestURI = '/services/apexrest/https:/veditechnologies-dev-ed.my.salesforce.com/leadactivity/getlist' ;  
       RestContext.request = req;
       RestContext.response = res;
       
       List<myActivityTask.cust_map> results = myActivityTask.doGetLead();
       
       system.Test.stopTest();
     
   }
   
}


Thanks