@isTest
private class SandboxPostRefreshTestCase {

    static Testmethod void testSandboxPostCopyScript() {

        Account accVar = new Account();
        accVar.Name ='Account Test';
        INSERT accVar;

        Contact conVar = new Contact();
        conVar.LastName ='Contact Test';
        conVar.AccountId =accVar.Id;
        conVar.Email = 'test@gmail.com';
        conVar.Other_Email__c = 'testother@gmail.com';
        INSERT conVar;

        Case casVar = new Case();
        casVar.Origin ='Email';
        casVar.Status = 'New';
        // casVar.ContactEmail = 'test@gmail.com';
        casVar.SuppliedEmail = 'testother@gmail.com';
        INSERT casVar;

        Campaign  camVar = new Campaign();
        camVar.Name ='test';
        INSERT camVar;

        CampaignMember newMemberVar = new CampaignMember();
        newMemberVar.CampaignId = camVar.Id;
        newMemberVar.ContactId = conVar.Id;
        // newMember.Email = 'test@gmail.com';
        INSERT newMemberVar;

        Lead leadVar = new Lead();
        leadVar.LastName = 'testsds';
        leadVar.Status = 'New';
        leadVar.Company = 'test';
        leadVar.Email = 'test@gmail.com';
        INSERT leadVar;

        Opportunity oppVar = new Opportunity();
        oppVar.Name = 'testsds';
        oppVar.AccountId = accVar.Id;
        oppVar.CloseDate = date.today();
        oppVar.StageName = 'Proposal';
        INSERT oppVar;

        Quote quoteVar = new Quote();
        quoteVar.Name = 'testsds';
        // quoteVar.Account = accVar.Id;
        quoteVar.OpportunityId = oppVar.Id;



        Test.startTest();

        PrepareSandboxPostCopy_Batch obj = new PrepareSandboxPostCopy_Batch();
        PrepareSandboxPostCopy_Batch.executeBatch();
      //  system.assertEquals(true, PrepareSandboxPostCopy_Batch.isSandbox());

        Test.stopTest();

    }
}

global class PrepareSandboxPostCopy_Batch implements Database.Batchable<sObject> {

    String query;
    String sObjectName;
    Map <String, List <String>> sObjectEmaiLFieldsMap = new Map <String, List <String>>();

    //Call this method from the class that implements the SandboxPostCopy Interface or from Developer console
    global static void executeBatch() {
        Map <String, List <String>> sObjectEmaiLFieldsMap = getsObjectEmaiLFields();

        if(!sObjectEmaiLFieldsMap.isEmpty()) {
            Database.executeBatch(new PrepareSandboxPostCopy_Batch(sObjectEmaiLFieldsMap));
        }
    }

    /** BATCHABLE INTERFACE IMPLEMENTATION STARTS **/
    global PrepareSandboxPostCopy_Batch(Map <String, List <String>> sObjectFieldsMap) {
        //Get First Key In Map
        sObjectName = new List<String> (sObjectFieldsMap.keySet()).get(0);

        sObjectEmaiLFieldsMap = sObjectFieldsMap;
        query = getSOQLString(sObjectName, sObjectEmaiLFieldsMap.get(sObjectName));
    }

    global Database.QueryLocator start(Database.BatchableContext BC) {
        return Database.getQueryLocator(query);
    }

    global void execute(Database.BatchableContext BC, List<sObject> scope) {

        for(sObject thisRecord : scope) {
            for(String thisField : sObjectEmaiLFieldsMap.get(sObjectName)) {
                String email = (String) thisRecord.get(thisField);
                if(String.isEmpty(email) || email.contains('.invalid') || email.contains('.noemail')) continue; //If empty or if contains .invalid then do not update
                thisRecord.put(thisField, email + '.invalid'); //Append invalid to the email
            }
        }
        Database.update(scope, false); //allow partial success
    }

    global void finish(Database.BatchableContext BC) {
        //Remove the sObject (First Key) once the records for the sObject processed successfully
        sObjectEmaiLFieldsMap.remove(sObjectName);
        executeBatch(sObjectEmaiLFieldsMap);
    }
    /** BATCHABLE INTERFACE IMPLEMENTATION ENDS **/

    public static Boolean isSandbox() {
        return [SELECT IsSandbox FROM Organization WHERE Id =: UserInfo.getOrganizationId()].IsSandbox;
    }

    private static void executeBatch(Map <String, List <String>> sObjectFieldsMap) {
        if(!sObjectFieldsMap.isEmpty()) {
            Database.executeBatch(new PrepareSandboxPostCopy_Batch(sObjectFieldsMap));
        }
    }

    private static String getSOQLString(String sObjectName, List<String> sObjectFields) {

        String soqlQuery = 'SELECT {!sObjectFields} FROM {!objectTypeName} WHERE {!conditionals}';

        List<String> conditionals = new List <String>();
        for (String thisField: sObjectFields) {
            conditionals.add(thisField + ' != NULL');
        }

        soqlQuery = soqlQuery.replace('{!sObjectFields}', String.join(sObjectFields, ' ,'));
        soqlQuery = soqlQuery.replace('{!objectTypeName}', sObjectName);
        soqlQuery = soqlQuery.replace('{!conditionals}', String.join(conditionals, ' OR '));

        if(!isSandbox()) soqlQuery = soqlQuery + ' LIMIT 0'; //For Non Sandbox (Production) Instance Do Not Update Records

        return soqlQuery;
    }

    //Get all Queryable Objects and it's email fields
    private static Map <String, List <String>> getsObjectEmaiLFields() {

        Map <String, List <String>> sObjectEmailFieldMap = new Map <String, List <String>>();

        //Only pass the selected object, dynamically getting all objects may exceed APEX CPU Limit
        List<SObjectType> sObjectsToUpdate = new List<SObjectType>{ Account.SObjectType,
                                                                    Contact.SObjectType,
                                                                    Case.SObjectType,
                                                                    CampaignMember.SObjectType,
                                                                    Lead.SObjectType,
                                                                    Opportunity.SObjectType,
                                                                    Quote.SObjectType };

        for(SObjectType sObjectType : sObjectsToUpdate) {

            //Describe sObject
            DescribeSObjectResult sObjectDescribe = sObjectType.getDescribe();

            String objectTypeName = sObjectDescribe.getName();

            //Skip objects we cannot query or update
            if(!sObjectDescribe.isQueryable() || !sObjectDescribe.isUpdateable()) continue;

            for(SObjectField sObjectField: sObjectDescribe.fields.getMap().values()) {

                DescribeFieldResult thisField = sObjectField.getDescribe();

                //Skip all non email fields
                if(thisField.getType() != Schema.DisplayType.EMAIL || !thisField.isFilterable() || !thisField.isUpdateable()) continue;

                if(sObjectEmailFieldMap.containsKey(objectTypeName)) {
                    sObjectEmailFieldMap.get(objectTypeName).add(thisField.getName());
                }
                else {
                    sObjectEmailFieldMap.put(objectTypeName, new List <String> {thisField.getName()});
                }
            }
        }
        return sObjectEmailFieldMap;
    }
}

Test.startTest();

Map<String, List<String>> sObjectFieldsMap = new Map<String, List<String>>();
sObjectFieldsMap.put('Account', new List<String>{'Name, BillingCity'}); //Add valid sObject and fields for code coverage
PrepareSandboxPostCopy_Batch obj = new PrepareSandboxPostCopy_Batch(sObjectFieldsMap);
PrepareSandboxPostCopy_Batch.executeBatch();

Test.stopTest();