Well-behaved objects - Objects First with Java: A Practical Introduction Using BlueJ - page 251

Exercise 7.18 Create a test class that has Comment as its reference class. Create a test
that checks whether the author and rating details are stored correctly after creation. Record
separate tests that check whether the upvote and downvote methods work as expected.

Exercise 7.19 Create tests for SalesItem that test whether the findMostHelpfulCom-
ment method works as expected. Note that this method returns a Comment object. During
your testing, you can use the Get button in the method result dialog to get the result object
onto the object bench, which then allows you to make further method calls and add assertions
for this object. This allows you to identify the comment object returned (e.g., by checking its
author). You can also assert that the result is null or not null , depending on what you expect.

7.4.4 Fixtures

As a set of test methods is built up, it is common to find yourself creating similar objects for
each one. For instance, every test of the SalesItem class will involve creating at least one
SalesItem and initializing it, often by adding one or more comments. An object or a group
of objects that is used in more than one test is known as a fixture. Two menu items associated
with a test class enable us to work with fixtures in BlueJ: Object Bench to Test Fixture and Test
Fixture to Object Bench. In your project, create two SalesItem objects on the object bench.
Leave one without any comments, and add two comments to the other. Now select Object
Bench to Test Fixture from SalesItemTest . The objects will disappear from the object bench,
and if you examine the source code of SalesItemTest , you will see that its setUp method
looks something like Code 7.3, where salesIte1 and salesIte2 have been defined as fields.

Concept:

A fixture is a set of
objects in a defined
state that serves
as a basis for unit
tests.

Code 7.3
Creating a fixture

/**
* Sets up the test fixture.
*
* Called before every test case method.
*/
@ Before
public void setUp()
{

salesIte1 = new SalesItem( "Java Book" , 12345);
salesIte2 = new SalesItem( "Other" , 123);
salesIte2.addComment( "Fred" , "too expensive" , 1);

}

The significance of the setUp method is that it is automatically called immediately before
every test method is called. (The @Before annotation above the method header ensures this.)
This means that the individual test methods no longer need to create their own versions of the
fixture objects.

Once we have a fixture associated with a test class, recording tests becomes significantly simpler.
Whenever we create a new test method, the objects from the fixture will automatically appear on
the object bench—there is no longer a need to create new test objects manually each time.