Question

I have a test case where I add an entity, update it and delete the same. Hence, the order of execution is important here. I want it to be :

1. Create
2. Update
3. Delete

Strangely, for just one test case ( out of 15) , JUnit executes it in the following order :

1. Delete
2. Update
3. Create .

How do I tell JUnit to execute them in a specific order ? In other cases, JUnit works totally fine ( executing serially ) . And why does JUnit behave weirdly in this one case ?

Relevant code snippet below :

    private static Date date;
    private static int entity;
    static Parking p;
    public ParkingTests(String name) {
       super(name);
    }
    public void testAdd() throws Exception {
           //Add code here
    }
    public void testUpdate() throws Exception {
            //update code here
    }
    public void testDelete() throws Exception {
            //delete code here
    }
  }

It gets weirder. I run a lot of test cases as part of a suite. If I run just the Parking case, the order is maintained. If I run it along with others, it is sometimes maintained, sometimes not !

Answer 1

Your kind of situation is awkward, as it feels bad to keep duplicating work in order to isolate the tests (see below) – but note that most of the duplication can be pulled out into setUp and tearDown (@Before, @After) methods, so you don’t need much extra code. Provided that the tests are not running so slowly that you stop running them often, it’s better to waste a bit of CPU in the name of clean testing.

public void testAdd() throws Exception {
      // wipe database
      // add something
      // assert that it was added
}
public void testUpdate() throws Exception {
      // wipe database
      // add something
      // update it
      // assert that it was updated
}
public void testDelete() throws Exception {
      // wipe database
      // add something
      // delete it
      // assert that it was deleted
}

The alternative is to stick everything into one test with multiple asserts, but this is harder to understand and maintain, and gives a bit less information when a test fails:

public void testCRUD() throws Exception {
      // wipe database
      // add something
      // assert that it was added
      // update it
      // assert that it was updated
      // delete it 
      // assert that it was deleted
}

Testing with databases or collections or storage of any kind is tricky because one test can always affect other tests by leaving junk behind in the database/collection. Even if your tests don’t explicitly rely on one another, they may still interfere with one another, especially if one of them fails.

Where possible, use a fresh instance for each test, or wipe the data, ideally in as simple a way as possible – e.g. for a database, wiping an entire table is more likely to succeed than a very specific deletion that you might accidentally get wrong.

Update: It’s usually better to wipe data at the start of the test, so one failed test run doesn’t affect the next run.