Installing SQL Server 2016 CTP2 (Community Technology Preview) to test Reporting Services (SSRS) is a bit of a deception: the installer does not contain the developer tools! They (SSDT-BI or Report Builder) are also not yet available as a separate download as of June 10th 2015.
This fact is not communicated anywhere by Microsoft, although there is a mention by the SQL Server Team on June 1st 2015 in reaction to user Dave's remark concerning this:
Dave, agree completely, the tools upgrade is coming."
Source:
http://blogs.technet.com/b/dataplatforminsider/archive/2015/05/27/sql-server-2016-first-public-preview-now-available.aspx
Or here by another user:
https://social.msdn.microsoft.com/Forums/sqlserver/en-US/fa8133bd-5cfa-4add-aa20-4c5442760d65/download-ssdtbi-samples-for-sql-server-2016?forum=ssdt
This prevents users from testing e.g. the new configurable parameter box.
For those still interested, the CTP can be found here:
https://www.microsoft.com/en-us/evalcenter/evaluate-sql-server-2016