I'll buck against this advice any day. I've never used SQLite for mocking but I've used HSQLDB for functional tests of an extensive ORM-derived DAOs that talked to Oracle in production in the past. It was pretty flawless. I.e. when running in Oracle emulation mode HSQLDB was pretty close to the real thing for our purposes. For a few tiny differences we had automatic script that would convert from Oracle schema creation file to HSQLDB "Oracle" schema creation file any time changes to the real schema were introduced.
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I'll buck against this advice any day. I've never used SQLite for mocking but I've used HSQLDB for functional tests of an extensive ORM-derived DAOs that talked to Oracle in production in the past. It was pretty flawless. I.e. when running in Oracle emulation mode HSQLDB was pretty close to the real thing for our purposes. For a few tiny differences we had automatic script that would convert from Oracle schema creation file to HSQLDB "Oracle" schema creation file any time changes to the real schema were introduced.
I was going to say this too: HSQLDB is more suitable, at least for me, testing environment than SQLite.
For Java, see my other comment for how to run real PostgreSQL or MySQL from unit tests: https://news.ycombinator.com/item?id=10003789