Drools testing with junit

Question

What is the best practice to test drools rules with junit?

Until now we used junit with dbunit to test rules. We had sample data that was put to hsqldb. We had couple of

Answer 1

A unit test with DBUnit doesn't really work. An integration test with DBUnit does. Here's why: - A unit test should be fast. -- A DBUnit database restore is slow. Takes 30 seconds easily. -- A real-world application has many not null columns. So data, isolated for a single feature, still easily uses half the tables of the database. - A unit test should be isolated. -- Restoring the dbunit database for every test to keep them isolated has drawbacks: --- Running all tests takes hours (especially as the application grows), so no one runs them, so they constantly break, so they are disabled, so there is no testing, so you application is full of bugs. --- Creating half a database for every unit test is a lot of creation work, a lot of maintenance work, can easily become invalid (with regards to validation which database schema's don't support, see Hibernate Validator) and ussually does a bad job of representing reality.

Instead, write integration tests with DBunit: - One DBunit, the same for all tests. Load it only once (even if you run 500 tests). -- Wrap each test in a transaction and rollback the database after every test. Most methods use propagation required anyway. Set the testdata dirty only (to reset it in the next test if there is a next test) only when propagation is requires_new. - Fill that database with corner cases. Don't add more common cases than are strictly needed to test your business rules, so ussually only 2 common cases (to be able to test "one to many"). - Write future-proof tests: -- Don't test the number of activated rules or the number of inserted facts. -- Instead, test if a certain inserted fact is present in the result. Filter the result on a certain property set to X (different from the common value of that property) and test the number of inserted facts with that property set to X.