Database cleanup after Junit tests

Question

I have to test some Thrift services using Junit. When I run my tests as a Thrift client, the services modify the server database. I am unable to find a good solution which can clean up the database after each test is run. Cleanup is important especially because the IDs need to be unique which are currently read form an XML file. Now, I have to manually change the IDs after running tests, so that the next set of tests can run without throwing primary key violation in the database. If I can cleanup the database after each test run, then the problem is completely resolved, else I will have to think about other solutions like generating random IDs and using them wherever IDs are required.

Edit: I would like to emphasize that I am testing a service, which is writing to database, I don't have direct access to the database. But since, the service is ours, I can modify the service to provide any cleanup method if required.

Answer 1

If you are using Spring, everything you need is the @DirtiesContext annotation on your test class.

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration("/test-context.xml")
@DirtiesContext(classMode = ClassMode.AFTER_EACH_TEST_METHOD)
public class MyServiceTest {
   ....
}

Answer 2

Unless you as testing specific database actions (verifying you can query or update the database for example) your JUnits shouldn't be writing to a real database. Instead you should mock the database classes. This way you don't actually have to connect and modify the database and therefor no cleanup is needed.

You can mock your classes a couple of different ways. You can use a library such as JMock which will do all the execution and validation work for you. My personal favorite way to do this is with Dependency Injection. This way I can create mock classes that implement my repository interfaces (you are using interfaces for your data access layer right? ;-)) and I implement only the needed methods with known actions/return values.

//Example repository interface.
public interface StudentRepository
{
   public List<Student> getAllStudents();
}

//Example mock database class.
public class MockStudentRepository implements StudentRepository
{
   //This method creates fake but known data.
   public List<Student> getAllStudents()
   {
      List<Student> studentList =  new ArrayList<Student>();
      studentList.add(new Student(...));
      studentList.add(new Student(...));
      studentList.add(new Student(...));

      return studentList;
   }
}

//Example method to test.
public int computeAverageAge(StudentRepository aRepository)
{
   List<Student> students = aRepository.GetAllStudents();
   int totalAge = 0;
   for(Student student : students)
   {
      totalAge += student.getAge();
   }

   return totalAge/students.size();
}

//Example test method.
public void testComputeAverageAge()
{
   int expectedAverage = 25; //What the expected answer of your result set is
   int actualAverage = computeAverageAge(new MockStudentRepository());

   AssertEquals(expectedAverage, actualAverage);
}

Answer 3

How about using something like DBUnit?

Answer 4

Spring's unit testing framework has extensive capabilities for dealing with JDBC. The general approach is that the unit tests runs in a transaction, and (outside of your test) the transaction is rolled back once the test is complete.

This has the advantage of being able to use your database and its schema, but without making any direct changes to the data. Of course, if you actually perform a commit inside your test, then all bets are off!

For more reading, look at Spring's documentation on integration testing with JDBC.