public PageReference sendBulkSMSToLeads(){
    List<Lead> matchingLeadsList = [Select MobilePhone from Lead where Status =:leadStatus and Intake_Month__c =:intakeMonth
                                    and Intake_Year__c =:intakeYear];
    Set<String> uniquePhoneNumberList = new Set<String>();
    if(matchingLeadsList != null && matchingLeadsList.size() > 0){
        String commaSeparatedMobileNumbers = '';
        for(Lead lead : matchingLeadsList){

            if(lead.MobilePhone != null && lead.MobilePhone != ''){
                if(!uniquePhoneNumberList.contains(lead.MobilePhone)){
                    uniquePhoneNumberList.add(lead.MobilePhone);
                    commaSeparatedMobileNumbers = commaSeparatedMobileNumbers + ',' + lead.MobilePhone;
                }
            }
        }

        if(commaSeparatedMobileNumbers.length() > 0){
            commaSeparatedMobileNumbers = commaSeparatedMobileNumbers.substring(1, commaSeparatedMobileNumbers.length());
        }

        String payLoad = 'username=global&password=muzztech&mobile=' +commaSeparatedMobileNumbers + '&sendername=SPJAIN&message='+message;
        Http h = new Http();
        HttpRequest req = new HttpRequest();
        req.setEndpoint('http://priority.muzztech.in/sms_api/sendsms.php');
        req.setMethod('POST');
        req.setBody(payLoad);
        HttpResponse res = h.send(req);

        ApexPages.Message myMsg = new  ApexPages.Message(ApexPages.Severity.INFO,'Bulk SMS initiated for ' + matchingLeadsList.size() + ' leads');
        ApexPages.addMessage(myMsg);

    }else{
        ApexPages.Message myMsg = new  ApexPages.Message(ApexPages.Severity.ERROR,'No matching leads found to send SMS');
        ApexPages.addMessage(myMsg);
    }
    return null;
}

static testMethod void sendBulkSMSToLeadsTest() {
    Test.startTest();
    SMSController ctrl = new SMSController();
    ctrl.leadStatus = 'Hot';
    ctrl.intakeMonth = 'January';
    ctrl.intakeYear = '2017';
    Lead leadObj = new Lead(LastName='Test', Email='unittest2@gmail.com', MobilePhone='7854945777', Status = 'Hot', LeadSource = 'Chat', Intake_Year__c = '2017', Intake_Month__c = 'January');
    insert leadObj;
    ctrl.sendBulkSMSToLeads();

    Test.stopTest();
    }