unit testing in a functional language

[mitch abaza <mitch.abaza@...>]

I come from a heavy TDD/OOP background and I'm finding it challenging to apply the same testing discipline to Lua.  Here's the problem domain I'm trying to tackle:

I have a bunch of "rules" (ie: functions) and I want to apply some of 
those rules to certain customer data. I have a configuration system that says, 
"When applying rules to data from customer X, use this set of rules." 

I've come up with three modules:

filterRulesLibrary == contains a list of available rules (functions)

configSystem == determines which rules should be applied for a given customer

filterRuleProvider = module that uses the two above modules to return a table of functions (rules) to the client application 
 
Sample Code

==========================================================
--5.2 module style
local filterRuleProvider ={}

filterRuleProvider = require("filterRules")
configSystem =require("configSystem ")

filterRuleProvider.assembleRules = function(facilityId)

    local filters = {}

    if ( configSystem .shouldFilterEmptyMessages(facilityId)) then
        table.insert(filters,filterRuleProvider.filterEmptyMessages)
    end

    return filters
  end

return filterRuleProvider
==========================================================

I'm told you can't do reference equality on functions.  If true, how would I test that the returned table contains a "reference" to the filterRuleProvider.filterEmptyMessages function?