1 files changed, 29 insertions, 0 deletions
diff --git a/core/tests/Drupal/Tests/UnitTestCase.php b/core/tests/Drupal/Tests/UnitTestCase.php
index 2257148d0698..b279bd1ed250 100644
--- a/core/tests/Drupal/Tests/UnitTestCase.php
+++ b/core/tests/Drupal/Tests/UnitTestCase.php
@@ -13,6 +13,7 @@ use Drupal\Core\StringTranslation\PluralTranslatableMarkup;
 use Drupal\TestTools\Extension\DeprecationBridge\ExpectDeprecationTrait;
 use Drupal\TestTools\Extension\Dump\DebugDump;
 use PHPUnit\Framework\Attributes\BeforeClass;
+use PHPUnit\Framework\MockObject\MockObject;
 use PHPUnit\Framework\TestCase;
 use Prophecy\PhpUnit\ProphecyTrait;
 use Symfony\Component\VarDumper\VarDumper;
@@ -210,4 +211,32 @@ abstract class UnitTestCase extends TestCase {
     return $class_resolver;
   }
 
+  /**
+   * Set up a traversable class mock to return specific items when iterated.
+   *
+   * Test doubles for types extending \Traversable are required to implement
+   * \Iterator which requires setting up five methods. Instead, this helper
+   * can be used.
+   *
+   * @param \PHPUnit\Framework\MockObject\MockObject&\Iterator $mock
+   *   A mock object mocking a traversable class.
+   * @param array $items
+   *   The items to return when this mock is iterated.
+   *
+   * @return \PHPUnit\Framework\MockObject\MockObject&\Iterator
+   *   The same mock object ready to be iterated.
+   *
+   * @template T of \PHPUnit\Framework\MockObject\MockObject&\Iterator
+   * @phpstan-param T $mock
+   * @phpstan-return T
+   * @see https://github.com/sebastianbergmann/phpunit-mock-objects/issues/103
+   */
+  protected function setupMockIterator(MockObject&\Iterator $mock, array $items): MockObject&\Iterator {
+    $iterator = new \ArrayIterator($items);
+    foreach (get_class_methods(\Iterator::class) as $method) {
+      $mock->method($method)->willReturnCallback([$iterator, $method]);
+    }
+    return $mock;
+  }
+
 }