Reuse spring application context across junit test classes

To add to Tomasz Nurkiewicz's answer, as of Spring 3.2.2 @ContextHierarchy annotation can be used to have separate, associated multiple context structure. This is helpful when multiple test classes want to share (for example) in-memory database setups (datasource, EntityManagerFactory, tx manager etc).

For example:

@ContextHierarchy({
  @ContextConfiguration("/test-db-setup-context.xml"),
  @ContextConfiguration("FirstTest-context.xml")
})
@RunWith(SpringJUnit4ClassRunner.class)
public class FirstTest {
 ...
}

@ContextHierarchy({
  @ContextConfiguration("/test-db-setup-context.xml"),
  @ContextConfiguration("SecondTest-context.xml")
})
@RunWith(SpringJUnit4ClassRunner.class)
public class SecondTest {
 ...
}

By having this setup the context that uses "test-db-setup-context.xml" will only be created once, but beans inside it can be injected to individual unit test's context

More on the manual: http://docs.spring.io/spring/docs/current/spring-framework-reference/html/testing.html#testcontext-ctx-management (search for "context hierarchy")

Yes, this is perfectly possible. All you have to do is to use the same locations attribute in your test classes:

@ContextConfiguration(locations = "classpath:test-context.xml")

Spring caches application contexts by locations attribute so if the same locations appears for the second time, Spring uses the same context rather than creating a new one.

I wrote an article about this feature: Speeding up Spring integration tests. Also it is described in details in Spring documentation: 9.3.2.1 Context management and caching.

This has an interesting implication. Because Spring does not know when JUnit is done, it caches all context forever and closes them using JVM shutdown hook. This behavior (especially when you have a lot of test classes with different locations) might lead to excessive memory usage, memory leaks, etc. Another advantage of caching context.