Testing java application, database layer, embeeded db, execute sql script - junit

Question

I need to write unit test cases for a java application using Junit.
I thought of using embedded database like H2, but the challenge i am facing is, i have multiple test classes, and i thought of writing a sql script file for creating tables and initializing data for test db.
But how do we ensure it runs only once before any test case?
If there are multiple test classes, we cannot write these scripts in every test class in a #BeforeClass method.
There should be some other way. My application uses Oracle db but for testing I thought of using H2.
Any suggestions would be really appreciated!

Answer 1

1) Like #BeforeClass that will run once at the beginning of the tests suite, there is #Before that will run before every test.
2) If you are doing a unit test to a certain class/piece of code, then it is better practice not work with a real DB, but with a mock DB that you inject into the code that you are testing and setting its behavior. A popular mocking framework is Mockito
So you can do things like that:
when(carsRepository.findById(id)).thenReturn(null);
when(carsRepository.findAllByCustomerName(customerName)).thenReturn(someCars);