Each unit test should check one specific piece of functionality. Do
not combine multiple, unrelated tests into a single testXXX( )
method.
Each test method can have as many assertXXX( )
calls as you like, but they can lead to problems:
public void testGame( ) throws BadGameException { Game game = new Game( ); Ship fighter = game.createFighter("001"); assertEquals("Fighter did not have the correct identifier", "001", fighter.getId( )); Ship fighter2 = game.createFighter("001"); assertSame("createFighter with same id should return same object", fighter, fighter2); assertFalse("A new game should not be started yet", game.isPlaying( )); }
This is a bad design because each assertXXX( )
method is testing an unrelated piece of functionality. If the first
assertEquals( )
fails, the remainder of the test
is not executed. When this happens, you won’t know
if the other tests are functional.
Example 4-2 shows a refactored test case that tests
various aspects of our game independently. We will see how to remove
the duplicated code in Recipe 4.6 when we talk
about setUp( )
and
tearDown( )
.
Example 4-2. Refactored tests
public void testCreateFighter( ) throws BadGameException { Game game = new Game( ); Ship fighter = game.createFighter("001"); assertEquals("Fighter did not have the correct identifier", "001", fighter.getId( )); game.shutdown( ); } public void testSameFighters( ) throws BadGameException { Game game = new Game( ); Ship fighter = game.createFighter("001"); Ship fighter2 = game.createFighter("001"); assertSame("createFighter with same id should return same object", fighter, fighter2); game.shutdown( ); } public void testGameInitialState( ) throws BadGameException { Game game = new Game( ); assertFalse("A new game should not be started yet", game.isPlaying( )); game.shutdown( ); }
With this approach, one test failure will not cause the remaining
assertXXX( )
statements to be skipped.
This issue raises the question: should a test method ever contain
more than one assertXXX( )
? The answer is a
definite yes! If you are testing a series of conditions in which
subsequent tests will always fail when the first fails, you may as
well combine all of the asserts in one test.
See Recipe 4.6 to learn how to create the
Game
object in the setUp( )
method and shutdown the game in the tearDown( )
method.
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