使用测试运行器进行两种不同的测试JUnit

Question

I have a class that I am testing using JUnitCore Test Runners to run the test. The program essentially removes every nth value from a linked list, it is very simple. I am testing:

1) See if the new list size is the size I expect it to be. 2) See if an element was removed that I know should have been. For example below I know that "Item 1" has been removed.

I have been tasked with making sure that 1) will pass and 2) will fail, and all of this works, but on running my code, my problems are:

1) It is not a very efficient test and could be improved. 2) When 1) is True and 2) is false (as in code below), the output is just "False", and I am not sure if this is right.

I have tried when both classes are true and it returns True.

• Code for testing

    import org.junit.Test; import org.junit.Ignore; import static org.junit.Assert.*; import java.util.LinkedList; public class PruneTest { @Test public void testListSize() { LinkedList <String> linkedlist = new LinkedList<String>(); linkedlist.add("Item 0"); linkedlist.add("Item 1"); linkedlist.add("Item 2"); linkedlist.add("Item 3"); linkedlist.add("Item 4"); linkedlist.add("Item 5"); linkedlist.add("Item 6"); linkedlist.add("Item 7"); linkedlist.add("Item 8"); linkedlist.add("Item 9"); Pruner prunes = new Pruner(); prunes.prune(linkedlist, 2); assertEquals(5, linkedlist.size()); } @Test public void testItemRemoved(){ LinkedList <String> linkedlist = new LinkedList<String>(); linkedlist.add("Item 0"); linkedlist.add("Item 1"); linkedlist.add("Item 2"); linkedlist.add("Item 3"); linkedlist.add("Item 4"); linkedlist.add("Item 5"); linkedlist.add("Item 6"); linkedlist.add("Item 7"); linkedlist.add("Item 8"); linkedlist.add("Item 9"); Pruner prunes = new Pruner(); prunes.prune(linkedlist, 2); assertTrue(linkedlist.contains("Item 1")); } } 

• Code for creating Test Runner

   import org.junit.runner.JUnitCore; import org.junit.runner.Result; import org.junit.runner.notification.Failure; public class PruneTestTwo { public static void main() { Result result = JUnitCore.runClasses(PruneTest.class); for (Failure failure : result.getFailures()) { System.out.println(failure.toString()); } System.out.println(result.wasSuccessful()); } } 

Answer 1

You can get more verbose and useful output from your tests using the alternative assertThat method with matchers, rather than the older assertEquals / assertTrue

For example you could combine your two tests above and get meaningful output about what's failing like this:

   @Test
   public void testListSize() {

    LinkedList <String> linkedlist = new LinkedList<String>();
    linkedlist.add("Item 0");
    linkedlist.add("Item 1");
    linkedlist.add("Item 2");
    linkedlist.add("Item 3");
    linkedlist.add("Item 4");
    linkedlist.add("Item 5");
    linkedlist.add("Item 6");
    linkedlist.add("Item 7");
    linkedlist.add("Item 8");
    linkedlist.add("Item 9");

    Pruner prunes = new Pruner();
    prunes.prune(linkedlist, 2);

    assertThat(linkedlist.size(), is(5));
    assertThat(linkedlist, hasItem("Item 1"));    
  }

Then when the second assertion fails, you'll get output similar to this (which is much easier to understand than a lonely false ):

java.lang.AssertionError: 
Expected: a collection containing "x"
     but: was "Item 0", was "Item 1", was "Item 2", was "Item 3", was "Item 4", was "Item 5", was "Item 6", was "Item 7", was "Item 8", was "Item 9"

You could improve it even more by making sure the pruned list is exactly what you expect - instead of checking the size and one item in it, you can check the size and every item (along with the order of the list) by using the contains matcher:

assertThat(linkedlist, contains("Item 0", "Item 2", "Item 4", "Item 6", "Item 8"));