Hi, I'm new to APEX and getting a little out of my depth. I have a few triggers that essentially prevent users from deleting records when they match critera. I've written the test class below and have 91% coverage in Sandbox. 

When i try to deploy into Production i get this error:

Code Coverage Failure
Your code coverage is 25%. You need at least 75% coverage to complete this deployment.

I'm aware it could be down to bad coding but Can anyone help?

@istest
public class TriggerTests{
@istest static void testOLITrigger() {
    System.Test.startTest();
Date ddate = Date.Today();
Account a2 = new Account(Name ='Test Account');
insert a2;
// Get the Standard PriceBook Id.
Id pricebookId = Test.getStandardPricebookId();       
Opportunity opp = new Opportunity(
    Name='Testing Opp',                            
    AccountId= a2.Id,
    StageName = 'Discovery',
    Type = 'New Business', 
    CurrencyIsoCode = 'USD',
    Region__c = 'New York',
    CloseDate = ddate);
insert opp;      
//Create your product
Product2 prod = new Product2(
     Name = 'TW Print',
    Family = 'The Week',
     Brand__c = 'The Week',
Ad_Type__c  = 'Display Advertising', 
    Media_Type__c = 'Print',
     ProductCode = 'TWP',
     isActive = true,
    CanUseRevenueSchedule = true
);
insert prod;
//Create your pricebook entry
PricebookEntry pbEntry = new PricebookEntry(
     Pricebook2Id = pricebookId,
     Product2Id = prod.Id,
     UnitPrice = 100.00,
     IsActive = true
);
insert pbEntry;
    //Create Line Item Details
Line_Item_Details__c LID = new Line_Item_Details__c(
    CurrencyIsoCode = 'USD',
    Print_Ad_Size__c = '1 Full Page',
    Quantity__c = 5,
    Rate__c = 123,
    Total_Net_Cost__c = 123*5,
    OppProductInvoiced__c = False
);
insert LID;       
//Create Opportunity Line Item. 
OpportunityLineItem oli = new OpportunityLineItem(
     OpportunityId = opp.Id,
     UnitPrice = 123,
     Quantity = 5,
     PricebookEntryId = pbEntry.Id,
    ServiceDate = ddate,
    Digital_End_Date__c = ddate +7,     
    Print_Frequency__c  = 'Consecutive Issues',
    Line_Item_Details__c = LID.id,
    Original_Total_Cost__c = 123*5,
    number_of_invoice_lines__c = 1
);
insert oli;  
//Create Test Issue
Issue__c Iss = new Issue__c(
    Name = 'Test Issue',
    Brand__c = 'The Week',
    Product_Code__c = 'TWM',
    On_Sale_Date__c = ddate - 7,
    Issue_counter__c = 2020001    
);
insert Iss;
//Create Insertion
Insertion__c Ins = new Insertion__c(
    Issue_lookup__c = Iss.id,
    Opportunity__c = opp.id,
    Line_Item_Details__C = LID.id
);
insert Ins;
//Create Opportunity Line Item Schedule. 
OpportunityLineItemSchedule olis = new OpportunityLineItemSchedule (
    OpportunityLineItemId = oli.id,
    ScheduleDate = ddate,
    Revenue =  123,
    Type = 'Revenue',
    Invoiced__c = TRUE
);
insert olis;   
  Try{
        olis.Revenue = 1234;
        olis.ScheduleDate = ddate + 2;
        update olis;       
    }
    catch(exception e){
              system.assert(e.getMessage().contains('You can not Amend this Schedule as it has been Invoiced'));                
}
    Try{
        delete olis;
    }
      catch(exception e){
                system.assert(e.getMessage().contains('You can not Delete this Schedule as it has been Invoiced'));                
}
    Try{
        delete oli;
    }
    catch(exception e){
                system.assert(e.getMessage().contains('You can not delete this Product as it has Invoiced Schedules'));  
    }
    Try{
        delete Ins;
    }
    catch(exception e){
                system.assert(e.getMessage().contains('You can not delete this Insertion as it has Closed'));  
    }          
System.Test.stopTest() ; 
}

//Test For Line Item Details Trigger    

@isTest static void testLIDTrigger() {
System.Test.startTest();
    //Create Line Item Details
    Line_Item_Details__c LID = new Line_Item_Details__c(
    CurrencyIsoCode = 'USD',
    Print_Ad_Size__c = '1 Full Page',
    Quantity__c = 5,
    Rate__c = 123,
    Total_Net_Cost__c = 123*5,
    OppProductInvoiced__c = TRUE
);
insert LID;
    
      try
    {
    delete LID;
        }
    catch(Exception e)
    { 
}
}
}