DisplayManagerTest.php

<?php

namespace Drupal\Tests\phpunit_example\Unit;

use Drupal\phpunit_example\DisplayInfoInterface;
use Drupal\phpunit_example\DisplayManager;
use Drupal\Tests\UnitTestCase;

/**
 * DisplayManager unit test with doubles.
 *
 * @ingroup phpunit_example
 *
 * @group phpunit_example
 * @group examples
 */
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'));
    }

}