Hanging test issue demonstration

Demonstrates the hanging test issue when a test annotated with @DataJpaTest is executed before a test annotated with @SpringBootTest.

Project structure

This project is a simple spring boot application using Spring Data JPA and Spring Data ReST build with maven. It also contains two IntelliJ Run/Debug configuration to execute the tests in different orders.

Issue

If the test workspace.domain.WorkspaceRepositoryTest annotated with @DataJpaTest is executed before the test workspace.api.rest.WorkspaceResourceTest annotated with @SpringBootTest the second tests hangs while its application context is started. Use the Run/Debug configuration JpaTestBeforeBootTest to reproduce the behaviour. If you execute both tests the other way round with the Run/Debug configuration BootTestBeforeJpaTest then the issue does not occure.

Workarounds

I figured out several workarounds to mitigate the issue which might also help to analyse the problem.

1. As I said above the issue is dependend on the execution order of the tests. Swapping the execution order solves the issue.
2. Removing the Spring Data ReST dependecy in the pom solves the issue.
3. Making the initialization of the application event publisher lazy in workspace.domain.Workspace.WorkspaceEventManager solves the issue.
4. Adding a mock listerner in workspace.domain.WorkspaceRepositoryTest solves the issue.

After the discussion of this topic on StackOverflow the most convenient workaround or even the solution is perhaps to move the configuration for @Asnyc into its own configuration class. So remove the @EnableAsnyc from Application and create a new class annotated with @Configuration and @EnableAsnc in the same package. This ensures that in the JPATest workspace.domain.WorkspaceRepositoryTest is disabled because Spring Boot does not consider configuration clases automatically when @DataJpaTest is used but if the application is started then @Asnyc is enabled because Spring Boot finds the new configuration via the component scan.

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Discussed in: https://stackoverflow.com/questions/63829138/spring-context-initialisation-hangs-when-executing-a-test-annotated-with-spring