I found that TO_DATE, TO_CHAR are not found in HSQLDB. Was wondering if anyone had a workaround for this. The team I am on uses HSQLDB as a test case database. But the actual Application will run against Oracle.
TO_DATE etc. are Oracle-specific SQL functions. They're not standard SQL so they don't exist in HSQLDB or other databases. To get around this, don't use those Oracle-specific functions, or use Oracle instead of HSQLDB for testing. If Oracle licenses are a problem, you could maybe use the free Oracle Express Edition for this purpose.
To make your application portable (you have this requirement, because it has to work on two database brands),
you have to use standard sql in your queries.
You should not need to_date.
If you have a select statement, you can retrieve date values by using ResultSet.getDate() and family.
If you have to use a date in the where clause, you should use PreparedStatement, and bind your date parameters.
Making an app database independent is not trivial. It's hard when you use frameworks that are specialised to do it, let alone without such a framework.
Databases behave differently (subtile - or sometimes not so subtile) even if you only use standard sql statements.
I don't know if it is a good idea to test your application with HSQLDB only, when production runs on Oracle.
I would certainly also include tests with an Oracle database.