Feature/issue 4 (#7)

* Added sample class implementation, LeadTriggerHandler.cls

* Added sample trigger implementation, Lead.trigger

* Added sample test class implementation, LeadTriggerHandler_Test.cls

Author: jongpie

src/classes/LeadTriggerHandler.cls

@@ -0,0 +1,34 @@
+public without sharing class LeadTriggerHandler extends TriggerHandler {
+
+    protected override void beforeInsert(List<SObject> newRecordList) {
+        List<Lead> newLeadList = (List<Lead>)newRecordList;
+
+        for(Lead newLead : newLeadList) {
+            this.setStatus(newLead);
+        }
+    }
+
+    protected override void beforeUpdate(List<SObject> updatedRecordList, Map<Id, SObject> updatedRecordListMap, List<SObject> oldRecordList, Map<Id, SObject> oldRecordMap) {
+        List<Lead> updatedLeadList = (List<Lead>)updatedRecordList;
+        Map<Id, Lead> oldLeadMap   = (Map<Id, Lead>)oldRecordMap;
+
+        for(Lead updatedLead : updatedLeadList) {
+            Lead oldLead = oldLeadMap.get(updatedLead.Id);
+
+            this.setStatus(updatedLead, oldLead);
+        }
+    }
+
+    private void setStatus(Lead updatedLead, Lead oldLead) {
+        // Add logic here. Methods can be overloaded to handle updates & inserts
+        if(updatedLead.Source != oldLead.Source) {
+            this.setStatus(updatedLead);
+        }
+    }
+
+    private void setStatus(Lead lead) {
+        // Add logic here. Methods should be simple & independent from each other (except for overloaded methods)
+        if(lead.LeadSource == 'Web') lead.Status = 'Open - Not Contacted';
+    }
+
+}

src/classes/LeadTriggerHandler.cls-meta.xml

@@ -0,0 +1,5 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<ApexClass xmlns="http://soap.sforce.com/2006/04/metadata">
+    <apiVersion>38.0</apiVersion>
+    <status>Active</status>
+</ApexClass>

src/classes/LeadTriggerHandler_Test.cls

@@ -0,0 +1,33 @@
+@isTest
+private class LeadTriggerHandler_Test {
+
+    @isTest
+    static void setStatus_Test() {
+        // All methods within the handler class (LeadTriggerHandler()) are protected or private, except for the exceute(), inherited from TriggerHandler.cls
+        // Your unit tests should test the outcome of your handler's classes methods.
+        // This lets you refactor your handler class at any point without any major dependencies since no variables or methods are public or global
+        // As long as your unit tests are THOROUGH, you can refactor your handler class as you see fit with confidence (as long as the tests still pass after you refactor)
+
+        // Create test data that should trigger (ha!) your method to run
+        Lead lead = new Lead(
+            Company    = 'My Test Company',
+            LastName   = 'Gillespie',
+            LeadSource = 'Web',
+            Status     = 'Closed'
+        );
+        // The test never calls LeadTriggerHandler - we let the Force.com platform handle executing the handler class
+        insert lead;
+
+        Test.startTest();
+
+        // If we setup our test correctly, then the handler class's setStatus() method should have updated the test lead
+        // Let's requery the lead so we can assert that the desired changes occurred
+        lead = [SELECT Id, LeadSource, Status FROM Lead WHERE Id = :lead.Id];
+        // Add asserts liberally like your life depends on it
+        System.assertEquals('Web', lead.LeadSource);
+        System.assertEquals('Open - Not Contacted', lead.Status);
+
+        Test.stopTest();
+    }
+
+}

src/classes/LeadTriggerHandler_Test.cls-meta.xml

@@ -0,0 +1,5 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<ApexClass xmlns="http://soap.sforce.com/2006/04/metadata">
+    <apiVersion>38.0</apiVersion>
+    <status>Active</status>
+</ApexClass>

src/triggers/Lead.trigger

@@ -0,0 +1,7 @@
+trigger Lead on Lead (before insert, before update, before delete, after insert, after update, after delete, after undelete) {
+
+    // Triggers should call all before & after operations. The code within the handler class can then implement any methods needed without updating the trigger
+    // Triggers should have no logic other than to call the corresponding handler class's execute method
+    new LeadTriggerHandler().execute();
+
+}

src/triggers/Lead.trigger-meta.xml

@@ -0,0 +1,5 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<ApexTrigger xmlns="http://soap.sforce.com/2006/04/metadata">
+    <apiVersion>38.0</apiVersion>
+    <status>Active</status>
+</ApexTrigger>