Salesforce Test Visual Apex Pages

1) Page.existingPageName

2) PageReference pageRef = new PageReference('partialURL');
PageReference pageRef = new PageReference('/apex/HelloWorld');

3) PageReference pageRef = new PageReference('fullURL');
PageReference pageRef = new PageReference('http://www.google.com');

4) PageReference pageRef = ApexPages.currentPage();

Executing page:
https://c.na7.visual.force.com/apex/SecondAccount


References

Displaying JIRA related information in Salesforce.com
http://www.customware.net/repository/pages/viewpage.action?pageId=62455956