Is there a way to fake a method response using Mock or Stubs?

Question

I have a helper method in my code called canQueryObject, and that method returns a boolean. I have some code that calls the method via the following line of code:

if(!myObjectHelper.canQueryObject(Schema.SObjectType.<<objectType>>)){ ... }

I'd like to test some scenarios where the scenario is false. Is there a way I can use Mock or Stubs in a unit-test to set canQueryObject to false?

Answer 1

I typically use a fairly simple pattern and don't bring in a framework. It would look something like the following:

public virtual with sharing class MyObjectHelper
{
    static MyObjectHelper instance = new MyObjectHelper();
    @TestVisible static void setMock(MyObjectHelper mock) { instance = mock; }

    public static Boolean canQueryObject(SObjectType sObjectType)
    {
        return instance.getCanQueryObject(sObjectType);
    }

    // the two method names cannot match or you will get a compile fail
    protected virtual Boolean getCanQueryObject(SObjectType sObjectType)
    {
        return sObjectType.getDescribe().isQueryable();
    }
}

Then in your test, you can have a mock return always true or always false, as you wish.

@IsTest
class MyObjectHelperTests
{
    class HelperMock extends MyObjectHelper
    {
        Boolean isQueryable = true;
        protected override Boolean getCanQueryObject(SObjectType sObjectType)
        {
            return isQueryable;
        }
    }

    @IsTest static void testCannotQuery()
    {
        HelperMock mock = new HelperMock();
        mock.isQueryable = false;
        MyObjectHelper.setMock(mock);

        Test.startTest();
            Boolean canQuery = MyObjectHelper.canQueryObject(...);
        Test.stopTest();

        system.assertEquals(false, canQuery, 'Some informative message');
    }
}