WV-4745: Add tests for module handler trait.

tests/src/Core/Extension/ModuleHandlerTraitTest.php

@@ -0,0 +1,71 @@
+<?php
+
+namespace drunomics\ServiceUtils\Tests\Core\Extension;
+
+use drunomics\ServiceUtils\Core\Extension\ModuleHandlerTrait;
+use Drupal\Core\DependencyInjection\Container;
+use Drupal\Core\Extension\ModuleHandlerInterface;
+
+/**
+ * @coversDefaultClass \drunomics\ServiceUtils\Core\Extension\ModuleHandlerTrait
+ * @group ServiceUtils
+ */
+class ModuleHandlerTraitTest extends \PHPUnit_Framework_TestCase {
+
+  use ModuleHandlerTrait;
+
+  /**
+   * The id of the trait's service.
+   *
+   * @var string
+   */
+  protected $serviceId = 'module_handler';
+
+  /**
+   * @covers ::getModuleHandler
+   */
+  public function testGetter() {
+    // Verify the container is used once and the right service is returned.
+    $service = $this->mockContainerWithFakeService(['calls' => 1]);
+    $this->assertsame($service, $this->getModuleHandler());
+    // Multiple calls should fetch the service from the container only once.
+    $this->getModuleHandler();
+  }
+
+  /**
+   * @covers ::setModuleHandler
+   */
+  public function testSetter() {
+    // Verify the set service is returned.
+    $this->mockContainerWithFakeService(['calls' => 0]);
+    $service = $this->prophesize()
+      ->willImplement(ModuleHandlerInterface::class)
+      ->reveal();
+    /** @var \Drupal\Core\Extension\ModuleHandlerInterface $service */
+    $this->setModuleHandler($service);
+    $this->assertsame($service, $this->getModuleHandler());
+  }
+
+  /**
+   * Helper to mock the container with a stub service.
+   *
+   * @param int[] $options
+   *   An array with the following keys:
+   *   - calls: The number of calls to get the service the mocked container
+   *     expects.
+   *
+   * @return object
+   *   The fake service returned by the container.
+   */
+  protected function mockContainerWithFakeService(array $options) {
+    $service = new \Stdclass();
+    $container = $this->prophesize(Container::class);
+    $prophecy = $container->get($this->serviceId);
+    /** @var \Prophecy\Prophecy\MethodProphecy $prophecy */
+    $prophecy->shouldBeCalledTimes($options['calls']);
+    $prophecy->willReturn($service);
+    \Drupal::setContainer($container->reveal());
+    return $service;
+  }
+
+}