jUnit test for addAll method

For my assignment, I have to develop several jUnit tests for the method:

 addAll(int index, Collection c)

This method is part of the class ArrayList - built in to java.

I figured out how to create the tests and run them in Eclipse IDE, but I'm a little confused as to e开发者_开发问答xactly how I'm supposed to develop the tests. Could I get an example that includes what I should have in a @before, @beforeClass, @after, @test method?

To make this clear, I understand the format of the methods...I just don't understand HOW to test this method.

http://download.oracle.com/javase/1.4.2/docs/api/java/util/ArrayList.html#addAll(java.util.Collection)

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So, what you need to test is that the method inserts all the elements in the passed Collection and that it inserts them into the appropriate position in the ArrayList.

Think of all the possible senerios and test each one.

1. start with empty arraylist
2. pass empty collection
3. use index of 0
4. use index > 0
5. etc, etc...

After the add, verify / assert that the ArrayList now has all the elements that it should have in the correct order / locations.

Also test the error cases with @Test(expected=...).

1. index < 0
2. index > arrayList.size()
3. null collection
4. come up with other ideas

Also... assertThat in combination with Hamcrest's IsIterableContainingInOrder would be helpful for verification.

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You will need to think of the behaviour you want to test, and then create a number of methods annotated with @Test to test aspects of that behaviour. Think about how should addAll behave. For example, if a collection passed to it, and an index of 0, then it should add all those elements in index 0 of ArrayList, followed by previously existing objects. So, in your test method, create an ArrayList, stick some objects in it, create a collection (c), stick some objects in it, call addAll on your arrayList with index 0 and collection (c), and assert that it has done what it was supposed to do...

(That's just an example, I am not sure what is the exact expected behaviour of addAll in your case)

Even better take a look at the wikipedia article Vakimshaar posted :)

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Stick with @Test and @Before Methods, the rest is probably not what you need.

Methods annotated with @Before get called every time before a method annotated with @Test is executed. You can use it to initialized stuff to a clean state which might be shared among multiple tests.

A starting point could be the following code (for more cases to test take a look at John's answer) and implement them yourself.

public class ArrayListTest {

    public ArrayList<String> list;

    @Before
    public void before() {
        // This the place where everything should be done to ensure a clean and
        // consistent state of things to test
        list = new ArrayList<String>();
    }

    @Test
    public void testInsertIntoEmptyList() {
        // do an insert at index 0 an verify that the size of the list is 1
    }

    @Test
    public void testInsertIntoListWithMultipleItems() {
        list.addAll(Arrays.asList("first", "second"));
        list.addAll(1, Arrays.asList("afterFirst", "beforeSecond"));

        // Verify that the list now contains the following elements
        // "first", "afterFirst", "beforeSecond", "second"
        List<String> theCompleteList = // put the expected list here
        // Use Assert.assertEquals to ensure that list and theCompleteList are indeed the same
    }
}

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Use annotation @Test to mark test method that should return void and should not accept arguments.

For most usages this is enough. But if you want to run specific code before or after each test use implement appropriate method and mark them with @Before and @After annotation.

If you need some code that runs before or after test case (the class where you implement several tests) annotate appropriate methods using @BeforeClass and @AfterClass method. Pay attention that these methods must be static, so "before" method is executed event before the default constructor of your test case. You can use this fact if you wish too.