class DisplayManagerTest

class DisplayManagerTest extends UnitTestCase {
  
  /**
   * Test for DisplayManager's DisplayableItemInterface handling.
   *
   * This method sets up a mock DisplayableItemInterface object
   * and then feeds it to a DisplayManager object to test
   * the behavior of DisplayManager.
   *
   * See the inline comments for a thorough walk-through.
   */
  public function testSimpleMockDisplayManager() {
    // Setting up:
    // Get a mock object belonging to our desired interface.
    // Note that we have to fully qualify the domain name
    // for PHPUnit's benefit.
    $mock = $this->createMock(DisplayInfoInterface::class);
    // Here we're illustrating that the mock object belongs to
    // our interface.
    $this->assertTrue($mock instanceof DisplayInfoInterface);
    // 'Program' our mock object to return a value for getDisplayName().
    // expects($this->any()) tells the mock to return this value any time
    // the method is called.
    $mock->expects($this->any())
      ->method('getDisplayName')
      ->willReturn('the display name');
    // Create a DisplayManager, the class we're actually testing here.
    $dm = new DisplayManager();
    // Give it the mocked info object.
    $dm->addDisplayableItem($mock);
    // Assert that our DisplayManager has exactly one display object (our mock).
    $this->assertEquals(1, $dm->countDisplayableItems());
    // Assert that the DisplayManager can find our mocked info object.
    $this->assertSame($mock, $dm->item('the display name'));
    // Assert that the DisplayManager can't find an info object
    // that it shouldn't have.
    $this->assertNull($dm->item('nonexistent'));
  }

}