Salesforce SOQL-Free Apex Tests with Selector Pattern

With Apex a Selector Pattern provides multiple benefits including

• A centralized place to query once, minimizing the number of queries
• The ability to test the queries in the Selector independent from the classes that utilize the Selector

Selector Patterns can allow for a configurable query. In the case below we configure with Custom Metadata

public class AccountSelector implements IAccountSelector {
    public List<Account> selectById(List<Id> accountIds){
        list<string> fieldList = new list<string>{ 'Id' };
        for (Account_Selector_Field__mdt asf : Account_Selector_Field__mdt.getAll().values())
            fieldList.add(asf.fieldname__c);
        String accountQuery = 'SELECT {0} FROM Account WHERE Id in (\'{1}\')'
        .replace('{0}',String.join(fieldList,','))
        .replace('{1}',String.join(accountIds,'\',\''));
        return Database.query(accountQuery);
    }
}

As indicated create an interface

public interface IAccountSelector {
    List<Account> selectById(List<Id> accountIds);
}

The below trigger handler class does not do anything functional but it is an example of how we can inject a Mock of the selector into the constructor. This allows query-free dml-free tests on the class.

public class AccountTriggerHandler {
    IAccountSelector accountSelector;
    public AccountTriggerHandler(){
        accountSelector = new AccountSelector();
    }
    
    public AccountTriggerHandler(IAccountSelector anAccountSelector{
        accountSelector = anAccountSelector;
    }
    
    public List<Account> getAccounts(Id accountId){
        return accountSelector.selectById(new List<Id>{ accountId});
    }
}

In the test, we can Mock the selection of data by creating a Mock class and generating the data we care about in the Mock.

@isTest
private class AccountTriggerHandlerTest{
    static testMethod void testGetAccounts() {
        AccountTriggerHandler ath = new AccountTriggerHandler(new AccountSelectorTest());
        List<Account> testResults = ath.getAccounts(’0011k0000000000AAA’);
        System.assertEquals(testResults[0].Id, '0011k0000000000AAA’);
    }
    class AccountSelectorTest implements IAccountSelector {
        public List<Account> selectById(List<Id> accountIds){
      return (List<Account>) JSON.deserialize(
                '[{"Id":"0011k0000000000AAA","Name":"testAccount"}]'
                , List<Account>.class
            );
        }
    }    
}

The test injects a selector mock now allowing for SOQL-free apex tests. The Selector pattern limits SOQL to tests that test the selector patterns, allowing us to scale with tests that don’t need awkward workaround to queries.