Apex class:/*




public class OpportunityTriggerHandlerverifiedIO {
    private static Boolean isExecuting = false;

    public static void handleClosedWonOpportunities(List<Opportunity> newOpportunities, Map<Id, Opportunity> oldOpportunityMap) {
        if (isExecuting) {
            // Skip trigger logic to avoid recursion
            return;
        }

        isExecuting = true;

        Set<Id> oppIds = new Set<Id>();
        Map<Id, APXT_Redlining__Contract_Agreement__c> oppToContractAgreementMap = new Map<Id, APXT_Redlining__Contract_Agreement__c>();
        
        for (Opportunity opp : newOpportunities) {
            // Check if the Opportunity is transitioning to 'Closed Won' and not a new Opportunity
            if (opp.StageName == 'Closed Won' && oldOpportunityMap.containsKey(opp.Id)) {
                oppIds.add(opp.Id);
            }
        }

        if (!oppIds.isEmpty()) {
            List<APXT_Redlining__Contract_Agreement__c> contractAgreements = [SELECT Id, Opportunity__c, APXT_Redlining__Status__c, Legal_review_completed__c,X3rd_Party_Paper__c, Customer_Signed_Date__c
                                                                            FROM APXT_Redlining__Contract_Agreement__c 
                                                                            WHERE CreatedDate > = 2023-08-13T15:13:08.000+0000 and Opportunity__c IN :oppIds];
            
           If(!contractAgreements.isEmpty()){
            
            for (APXT_Redlining__Contract_Agreement__c c : contractAgreements) {
                // Build the map of Opportunity Ids to Contract Agreement records
                oppToContractAgreementMap.put(c.Opportunity__c, c);
            }
            
            for (Opportunity opp : newOpportunities) {
                // Check if the Opportunity is transitioning to 'Closed Won' and has an existing Contract Agreement
                if (opp.StageName == 'Closed Won' && oppToContractAgreementMap.containsKey(opp.Id)) {
                    APXT_Redlining__Contract_Agreement__c contractAgreement = oppToContractAgreementMap.get(opp.Id);
                    
                    // Check if the contract agreement is active and not verified
                    if (contractAgreement.APXT_Redlining__Status__c == 'Active' && !contractAgreement.Legal_review_completed__c && contractAgreement.X3rd_Party_Paper__c == true )
                    //if (contractAgreement.APXT_Redlining__Status__c == 'Active' && !contractAgreement.Legal_review_completed__c && contractAgreement.X3rd_Party_Paper__c == true)||(contractAgreement)
                    {
                        opp.addError('Third party paper must be approved by Legal, please submit a "Legal Case".');
                    }
                    
                    else if((contractAgreement.APXT_Redlining__Status__c == 'Active'&& contractAgreement.Customer_Signed_Date__c==null)||(!(contractAgreement.APXT_Redlining__Status__c == 'Active')))
                    {
                        opp.addError('"To ‘Closed won’ the Opportunity, the Contract must be an active Contract Agreement and the customer must be signed".');
                    }
                
                }
                else if (opp.StageName == 'Closed Won' && !oppToContractAgreementMap.containsKey(opp.Id)) {
                    opp.addError('Closed Won Opportunity must have a contract agreement.');
                }
            }
        }
        }

        isExecuting = false;
    }
}

Trigger:

Trigger OpportunityTriggerHandlerverifiedIO on Opportunity (before update) {
    OpportunityTriggerHandlerverifiedIO.handleClosedWonOpportunities(Trigger.new, Trigger.oldMap);
}

Test class:
@isTest
private class OpportunityTriggerHandlerverifiedIOTest {
    @isTest
    static void testOpportunityTriggerHandler() {
        // Create test data
        Opportunity testOpportunity = new Opportunity(
            Name = 'Test Opportunity1',
            StageName = 'Sales Meeting Set',
            CloseDate = Date.today(),
            Start_Date__c=Date.today(),
            End_Date__c =Date.today(),
            Contact_Role_added__c = true,
            Billing_Term__c = 'Net 30',
            Type='New Logo',
            Billing_Account_Name__c='Test Account',
            Billing_Contact_Name__c='Test contact name',
            Billing_Email__c='test@gmail.com',
            Billing_Street__c='1234 test street',
            Billing_Postal_Code__c='75046',
            Billing_Country__c='US',
            Billing_City__c='Dallas',
            Deal_Term_In_Months__c='12',
            Is_timeframe_to_launch_within_30_days__c='Yes'
        );
        insert testOpportunity;

        APXT_Redlining__Contract_Agreement__c contract = new APXT_Redlining__Contract_Agreement__c(
            Opportunity__c = testOpportunity.Id,
            APXT_Redlining__Status__c = 'Active',
             Legal_review_completed__c = true,
            X3rd_Party_Paper__c = true,
            Customer_Signed_Date__c=Date.today()
        );
        insert contract;

     // Update the Opportunity to trigger the trigger
        testOpportunity.StageName = 'Closed Lost';
        testOpportunity.Reason_Lost__c = 'Went with Competitor – Price';
        try {
            Test.startTest();
            update testOpportunity;
            Test.stopTest();
            // If no exception is thrown, the test should fail
            //System.assert(false, 'Expected DMLException but no exception was thrown.');
        } catch (DmlException e) {
            // Assert the error message for Closed Lost Opportunity
            
            
             Boolean expectedExceptionThrown =  e.getMessage().contains('Closed Won Opportunity must have a contract agreement') ? true : false;
           System.AssertEquals(expectedExceptionThrown, true);          
            //System.assertEquals('Closed Won Opportunity must have a contract agreement.', e.getMessage());
        }
        

        // Update the Opportunity again to meet the conditions
        testOpportunity.StageName = 'Closed Won';
        try {
          //  Test.startTest();
            update testOpportunity;
           // Test.stopTest();
            // If no exception is thrown, the test should fail
            //System.assert(false, 'Expected DMLException but no exception was thrown.');
        }catch (DmlException e) {
    System.debug('Caught Exception Message: ' + e.getMessage());
    System.assertEquals('Third party paper must be approved by Legal, please submit a "Legal Case".', e.getMessage());
}

        
        
         

        // Update the Contract Agreement to meet the conditions
        contract.Verified_Signed_IO__c = true;
        update contract;

        // Update the Opportunity again to satisfy the conditions
        testOpportunity.StageName = 'Closed Won';
        try {
            //Test.startTest();
            update testOpportunity;
           // Test.stopTest();
            // If an exception is thrown, the test should fail
            System.assert(true, 'No exception should be thrown.');
        } catch (DmlException e) {
            // If an exception is thrown, the test should fail
            System.assert(false, 'No exception should be thrown.');
        }
    }
}


Above test class is covering only 53%. I have updated the lines in bold which are not covered. Can anyone help me fix this code coverage issue