Use the IBExpertDemoDB for benchmark testing. The UDFs and SQLs necessary to generate the demo database can be found in the IBExpert Developer Studio's /IBExpertDemoDB directory. The documentation lists the simple steps needed to generate a demo database to the size of your choice.
The IBExpert Benchmarks article illustrates in detail how to utilize this valuable function as a sample web shop.
In the subdirectory, \IBExpertDemoDB, you will find a script, db1_30.sql, which you an use to create a Firebird 3.0 database. Among other things this includes a Soundex function as a stored procedure, as a stored function and as a package. By these means you can create your own functions in Firebird 3.0 or using your own UDF, and use them in SQL as if they were an internal function.
Furthermore there is a basic implementation for a materialized view alternative in this script, which can also be used with older Firebird versions.
By combining a view with a static table it is possible to avoid calculating complex result sets each and every time, and only recalculate them following expiry of specified time intervals.