Can't access related record in test

Question

I have a visualforce page which is displaying a list of opportunities.

The page is working as expected - no problems.

The problem is that when testing I can't access the account which is associated with the opportunity. It displays on the visualforce page, but seemingly isn't set when running the test.

Controller:

public class showGuideExcel {

    public List <opportunity> oppList {get; set;}        


    public showGuideExcel () {
        string groupId = ApexPages.currentPage().getParameters().get('id');
        oppList = [SELECT account.name, account.website, account.billingCountry
               FROM opportunity WHERE group__c = :groupId and stageName = 'Contract Returned'];         
    }
}

Test:

@isTest
public class showGuideExcelTest {
    @isTest
    public static void retrieveCorrectInfo(){

        group__c testGroup = new group__c();
        insert testGroup;
        account testAccount = new Account(billingStreet ='testStreet',
                                          billingCity = 'Test City',
                                          billingState = 'Test State',
                                          billingCountry = 'Test Country',
                                          name = 'Test Account'
                                         );
        insert testAccount;
        opportunity testOpportunity = new Opportunity(stageName = 'Contract Returned',
                                                      name = 'Test Opportunity',
                                                      closeDate = System.today(),
                                                      group__c = testGroup.id,
                                                      account = testAccount
                                                     );
        insert testOpportunity;

        ApexPages.currentPage().getParameters().put('id', testGroup.id);

        System.debug(testAccount);
        System.debug(testOpportunity);
        System.debug(testOpportunity.account);
        // THE ABOVE ALL RETURN CORRECTLY
        showGuideExcel controller = new showGuideExcel();
        System.debug(controller.oppList);
        System.debug(controller.oppList[0]);
        System.debug(controller.oppList[0].account.name);
        System.assertEquals('Test Account', controller.oppList[0].account.name);
        // TEST FAILS - System.AssertException: Assertion Failed: Expected: Test Account, Actual: null
    }
}

Answer 1

The form of DML you're using, where you assign an sObject to the relationship property, is designed for adding related records using an external Id.

opportunity testOpportunity = new Opportunity(stageName = 'Contract Returned',
                                              name = 'Test Opportunity',
                                              closeDate = System.today(),
                                              group__c = testGroup.id,
                                              account = testAccount
                                             );

To relate the Opportunity to the Account using the regular Id field, set

AccountId = testAccount.Id

that is, directly assign the Id of the related record to the lookup field.

See Inserting Related Records for more.