--- /dev/null
+<?php
+
+namespace Drupal\Tests;
+
+use Drupal\Core\Extension\ExtensionDiscovery;
+
+/**
+ * Allows test classes to require Drupal modules as dependencies.
+ *
+ * This trait is assumed to be on a subclass of \PHPUnit_Framework_TestCase, and
+ * overrides \PHPUnit_Framework_TestCase::checkRequirements(). This allows the
+ * test to be marked as skipped before any kernel boot processes have happened.
+ */
+trait TestRequirementsTrait {
+
+ /**
+ * Returns the Drupal root directory.
+ *
+ * @return string
+ */
+ protected static function getDrupalRoot() {
+ return dirname(dirname(substr(__DIR__, 0, -strlen(__NAMESPACE__))));
+ }
+
+ /**
+ * Check module requirements for the Drupal use case.
+ *
+ * This method is assumed to override
+ * \PHPUnit_Framework_TestCase::checkRequirements().
+ *
+ * @throws \PHPUnit_Framework_SkippedTestError
+ * Thrown when the requirements are not met, and this test should be
+ * skipped. Callers should not catch this exception.
+ */
+ protected function checkRequirements() {
+ parent::checkRequirements();
+
+ $root = static::getDrupalRoot();
+
+ // Check if required dependencies exist.
+ $annotations = $this->getAnnotations();
+ if (!empty($annotations['class']['requires'])) {
+ $this->checkModuleRequirements($root, $annotations['class']['requires']);
+ }
+ if (!empty($annotations['method']['requires'])) {
+ $this->checkModuleRequirements($root, $annotations['method']['requires']);
+ }
+ }
+
+ /**
+ * Checks missing module requirements.
+ *
+ * Iterates through a list of requires annotations and looks for missing
+ * modules. The test will be skipped if any of the required modules is
+ * missing.
+ *
+ * @param string $root
+ * The path to the root of the Drupal installation to scan.
+ * @param string[] $annotations
+ * A list of requires annotations from either a method or class annotation.
+ *
+ * @throws \PHPUnit_Framework_SkippedTestError
+ * Thrown when the requirements are not met, and this test should be
+ * skipped. Callers should not catch this exception.
+ */
+ private function checkModuleRequirements($root, array $annotations) {
+ // drupal_valid_ua() might not be loaded.
+ require_once $root . '/core/includes/bootstrap.inc';
+
+ // Make a list of required modules.
+ $required_modules = [];
+ foreach ($annotations as $requirement) {
+ if (strpos($requirement, 'module ') === 0) {
+ $required_modules[] = trim(str_replace('module ', '', $requirement));
+ }
+ }
+
+ // If there are required modules, check if they're available.
+ if (!empty($required_modules)) {
+ // Scan for modules.
+ $discovery = new ExtensionDiscovery($root, FALSE);
+ $discovery->setProfileDirectories([]);
+ $list = array_keys($discovery->scan('module'));
+ $not_available = array_diff($required_modules, $list);
+ if (!empty($not_available)) {
+ throw new \PHPUnit_Framework_SkippedTestError('Required modules: ' . implode(', ', $not_available));
+ }
+ }
+ }
+
+}