FinancialForce Posting via checkbox

Invoice_PostAction.trigger

trigger Invoice_PostAction on c2g__codaInvoice__c (after insert, after update) {
    List<c2g.CODAAPICommon.Reference> toPost = new List<c2g.CODAAPICommon.Reference>();
    for(c2g__codaInvoice__c document:Trigger.new){
        if( document.Action_PostDocument__c == true ){
            if(document.c2g__invoiceStatus__c != 'In Progress'){
                System.debug(LoggingLevel.Warn,'Cannot post invoice, invoice is '+document.c2g__invoiceStatus__c);
            }else{
                c2g.CODAAPICommon.Reference ref = new c2g.CODAAPICommon.Reference();
                ref.id = document.id;
                toPost.add(ref);
            }
        }
    }
    if(toPost.size() > 0){
        List<sObject> postedInvoices = new List<sObject>();
        for(c2g.CODAAPICommon.Reference ref:toPost){ //post individually in order to only add errors to actually faled records
            postedInvoices.add(
                new c2g__codaInvoice__c(id = ref.id, Action_PostDocument__c = false)
            );
            try{
                c2g.CODAAPISalesInvoice_6_0.PostInvoice(null,ref);
            }catch(Exception e){
                Trigger.newMap.get(ref.id).addError('Failed to post document: '+e.getMessage());
            }
        }
        update postedInvoices; //uncheck the action: post box
    }
}

PostAction_Test.cls

@isTest
private class PostAction_Test{
    static final boolean softFail = false; //if true tests will fail softly - that is they will not be marked as failed but may not contribute full code coverage
    @isTest(seeAllData=true)
    static void invoiceTest(){
        try{
            Account customerAccount = [SELECT id FROM Account WHERE c2g__CODAAccountsReceivableControl__c != null LIMIT 1];
            Product2 product = [SELECT product2.id FROM PricebookEntry WHERE product2.c2g__CODASalesRevenueAccount__c != null AND product2.isActive = true LIMIT 1].product2;
            c2g__codaInvoice__c newInvoice = new c2g__codaInvoice__c(
                c2g__Account__c = customerAccount.id,
                c2g__InvoiceDate__c = Date.today()
                
            );
            insert newInvoice;
            List<c2g__codaInvoiceLineItem__c> newInvoiceLines = new List<c2g__codaInvoiceLineItem__c>{
                new c2g__codaInvoiceLineItem__c(
                    c2g__Invoice__c = newInvoice.id,
                    c2g__Product__c = product.id
                )
            };
            insert newInvoiceLines;
            
            //Post it!
            update new c2g__codaInvoice__c(id = newInvoice.id, Action_PostDocument__c = true);
        }catch(Exception e){
            if(softFail)
                System.debug(LoggingLevel.Error,'Soft fail enabled. Test marked as passed but it really failed with '+e.getMessage());
            else
                throw e;
        }
    }
}