Reuse spring application context across junit test classes

Question

We've a bunch of JUnit test cases (Integration tests) and they are logically grouped into different test classes.

We are able to load Spring application context once per test class and re-use it for all test cases in a JUnit test class as mentioned in http://static.springsource.org/spring/docs/current/spring-framework-reference/html/testing.html

However, we were just wondering if there is a way to load Spring application context only once for a bunch of JUnit test classes.

FWIW, we use Spring 3.0.5, JUnit 4.5 and use Maven to build the project.

Answer 1

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.

Answer 2

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")