Simple class to try and destroy all records in a Salesforce instance. Does not currently destroy Apex, or Visualforce, or Lightning components. It probably will never do the latter, I'm not sure I want it to do the former. Does not destroy custom metadata, but I'm looking into it. TODO: Parameters to avoid limits.

DestroyAllTheThings.cls

public class DestroyAllTheThings {
	

	public DestroyAllTheThings() {}

	
	public void destroySimpleCRMStuff() {

		//First clear out known dependents, leads and cases etc.

		List<Case> cases = [SELECT ID from Case];
		delete cases;

		List<Lead> leads = [SELECT ID From Lead];
		delete leads;

		List<Opportunity> opportunities = [SELECT ID From Opportunity];
		delete opportunities;

		List<Contact> contacts = [SELECT ID from Contact];
		delete contacts;

		List<Account> accounts = [SELECT ID from Account];
		delete accounts;
	}

	public void destroyAsMuchAsPossible() {
		//ok, now we can go and dynamically delete **everything** else
		Map<String, Schema.SObjectType> globalDescribe = Schema.getGlobalDescribe(); 
		Set<String> sobjects = globalDescribe.keySet();
		for(String so : sobjects) {
			
            //not allowed in DML
            //or has other restrictions where parent/dependents need to be removed first
            //or simply does not support query
            //or to support our code later
            if(globalDescribe.get(so).getDescribe().isDeletable() && globalDescribe.get(so).getDescribe().isQueryable()
               && so != 'EmailTemplate' && so != 'Vote' && so != 'ContentDocumentLink'
               && so != 'AuthSession' && so != 'ApexLog' && so != 'ObjectPermissions' && so != 'FieldPermissions'
               && so != 'IdeaComment') { 
                
                String soql = 'SELECT ID FROM '+so+' ';
				
                /* ApexClass not part of this ... not deleteable/queryable from Describe?  But AuthSession is?
            	if(so == 'ApexClass') { //don't delete this class
					soql = 'SELECT ID from ApexClass where Name != \'DestroyAllTheThings\' ';
					System.debug(soql);
				} */


				List<SObject> current_objects = Database.query(soql);
			
                try {
                    delete current_objects;
                } catch (System.DmlException e) {
                    System.debug(so + ' could not be deleted');
                    }
            
            }
            
            
		}
	}

	public void deleteApexAnd


	public void reallyDestroyAllTheThings() {
		destroySimpleCRMStuff();

		destroyAsMuchAsPossible();

	}

}