void方法的单元测试应该如何？

Question

I wrote the program that simulates the basket in the shop. The user is able to add and remove items from the basket. Now, I am wondering, how the unit test for my (void) methods should look like. I am using the JUnit 4.

I have tried to change my addItem method to return the boolean type, instead of returning nothing. With that I am able to write simple Assert.assertTrue(basket.add...) . But I do not know, how the unit test for the void method should be written.

public boolean addItem(Item item) {
    if (orderedItems.containsKey(item)) {
        Integer currItemCount = orderedItems.get(item);
        orderedItems.replace(item, currItemCount, currItemCount + 1);
        return true;
    } else {
        orderedItems.put(item, 1);
        return true;
    }
}

public void addItem(Item item) {
    if (orderedItems.containsKey(item)) {
        Integer currItemCount = orderedItems.get(item);
        orderedItems.replace(item, currItemCount, currItemCount + 1);
    } else {
        orderedItems.put(item, 1);
    }
}

Answer 1

Note that the boolean is helpless in your first version since it always return true . Besides, adding a boolean will really not help you to unit test your code since that is too shallow. So you should stick to your original idea (without boolean).

About your question : yes the addItem() method does not return anything but if you can add items in the basket, you very probably want to read them too.
The simplest way of testing add() is relying on a get()/find() method.
And reversely.

You could write something like that for a test with a item not present in the basket :

@Test
public void addItem_given_item_not_present_then_getAll_retrieves_it() {
   basket.addItem(new Item("foo"));
   Map<Item, Integer> items = basket.getAll();
   // assert items contains 1 element with 1 occurrence and with the foo name
}

And you should of course write other test scenarios.