How to test New behavior of a custom controller extension

Question

I have a Parent__c and Child__c object with Child records using a custom Controller Extension and Visualforce page for EDIT and NEW.

Testing this controller extension for existing Child__c records is straight forward..

@isTest
private static void saveChangesToExistingChildRecord() {

    // Setup
    Parent__c parent = insertParent();
    Child__c existingChild = insertChild(parent);

    // Execute
    ApexPages.StandardController stdCtrl = new ApexPages.StandardController(existingChild);
    Child_CtrlExt ctrlExt = new Child_CtrlExt(stdCtrl);

    PageReference customEditPage = Page.childEdit;
    customEditPage.getParameters().put('id', existingChild.Id);
    ctrlExt.save();

    // Verify
    ...
}

... but how can I do this for new records (meaning the page called for New)?

@isTest
private static void newChildIsSaved() {

    // Setup
    Parent__c parent = insertParent();
    Child__c existingChild = null;

    // Execute
    // ???
    ApexPages.StandardController stdCtrl = new ApexPages.StandardController(existingChild);
    Child_CtrlExt ctrlExt = new Child_CtrlExt(stdCtrl);

    PageReference customEditPage = Page.childEdit;
    // ???
    customEditPage.getParameters().put('id', existingChild.Id); 
    ctrlExt.save();

    // Verify
    ...
}

Passing around null values to mimic a not yet existing object does not seem to work. When I look at the page params I see a cryptic LKID param, which seems to pass information about the parent object.

Answer 1

StandardController has a constructor taking an SObject, but it's not required that the passed object exists in the database. Thanks to this you can simply say:

new ApexPages.StandardController(new Child__c(parent__c = parent.Id));

Controller extensions should call standardController.getRecord() or standardController.getId() to access record's ID, and understand that it will be blank if a record is just created.

Answer 2

Let's imagine you have an existing Parent_c on a detail page and in the related list Child_c of Parent__c, there is a New button.

When the New button is clicked, the controller extension for Child_c is invoked. The controller will be passed an object of Child_c with parent__c populated to point at the instance of the parent object.

Thus, the test class is as follows:

@isTest
private static void newChildIsSaved() {

// Setup
Parent__c parent = insertParent();
Child__c existingChild = new Child__c(parent__c = parent.id)

// Execute
Test.setCurrentPageReference(Page.childEdit);
ApexPages.StandardController stdCtrl = new ApexPages.StandardController(existingChild);
Child_CtrlExt ctrlExt = new Child_CtrlExt(stdCtrl);

ctrlExt.save();

// Verify
...

}