.../tests/Traits/ContentModerationTestTrait.php    | 91 ++++++++++++++++++++++
 tests/src/Functional/ResourceTestBase.php          |  7 +-
 2 files changed, 96 insertions(+), 2 deletions(-)

diff --git a/src/BackwardCompatibility/tests/Traits/ContentModerationTestTrait.php b/src/BackwardCompatibility/tests/Traits/ContentModerationTestTrait.php
new file mode 100644
index 0000000..310bcfb
--- /dev/null
+++ b/src/BackwardCompatibility/tests/Traits/ContentModerationTestTrait.php
@@ -0,0 +1,91 @@
+<?php
+
+namespace Drupal\jsonapi\BackwardCompatibility\tests\Traits;
+
+use Drupal\workflows\Entity\Workflow;
+
+/**
+ * Trait ContentModerationTestTraint.
+ *
+ * @see \Drupal\Tests\content_moderation\Traits\ContentModerationTestTrait
+ * @todo Remove when JSON:API requires Drupal >=8.6
+ */
+trait ContentModerationTestTrait {
+
+  /**
+   * Creates the editorial workflow.
+   *
+   * @return \Drupal\workflows\Entity\Workflow
+   *   The editorial workflow entity.
+   */
+  protected function createEditorialWorkflow() {
+    $workflow = Workflow::create([
+      'type' => 'content_moderation',
+      'id' => 'editorial',
+      'label' => 'Editorial',
+      'type_settings' => [
+        'states' => [
+          'archived' => [
+            'label' => 'Archived',
+            'weight' => 5,
+            'published' => FALSE,
+            'default_revision' => TRUE,
+          ],
+          'draft' => [
+            'label' => 'Draft',
+            'published' => FALSE,
+            'default_revision' => FALSE,
+            'weight' => -5,
+          ],
+          'published' => [
+            'label' => 'Published',
+            'published' => TRUE,
+            'default_revision' => TRUE,
+            'weight' => 0,
+          ],
+        ],
+        'transitions' => [
+          'archive' => [
+            'label' => 'Archive',
+            'from' => ['published'],
+            'to' => 'archived',
+            'weight' => 2,
+          ],
+          'archived_draft' => [
+            'label' => 'Restore to Draft',
+            'from' => ['archived'],
+            'to' => 'draft',
+            'weight' => 3,
+          ],
+          'archived_published' => [
+            'label' => 'Restore',
+            'from' => ['archived'],
+            'to' => 'published',
+            'weight' => 4,
+          ],
+          'create_new_draft' => [
+            'label' => 'Create New Draft',
+            'to' => 'draft',
+            'weight' => 0,
+            'from' => [
+              'draft',
+              'published',
+            ],
+          ],
+          'publish' => [
+            'label' => 'Publish',
+            'to' => 'published',
+            'weight' => 1,
+            'from' => [
+              'draft',
+              'published',
+            ],
+          ],
+        ],
+      ],
+    ]);
+    $workflow->save();
+    return $workflow;
+  }
+
+}
diff --git a/tests/src/Functional/ResourceTestBase.php b/tests/src/Functional/ResourceTestBase.php
index 5b770be..751e808 100644
--- a/tests/src/Functional/ResourceTestBase.php
+++ b/tests/src/Functional/ResourceTestBase.php
@@ -27,13 +27,13 @@ use Drupal\Core\TypedData\TypedDataInternalPropertiesHelper;
 use Drupal\Core\Url;
 use Drupal\field\Entity\FieldConfig;
 use Drupal\field\Entity\FieldStorageConfig;
+use Drupal\jsonapi\BackwardCompatibility\tests\Traits\ContentModerationTestTrait;
 use Drupal\jsonapi\JsonApiResource\NullEntityCollection;
 use Drupal\jsonapi\Normalizer\HttpExceptionNormalizer;
 use Drupal\jsonapi\JsonApiResource\JsonApiDocumentTopLevel;
 use Drupal\jsonapi\ResourceResponse;
 use Drupal\path\Plugin\Field\FieldType\PathItem;
 use Drupal\Tests\BrowserTestBase;
-use Drupal\Tests\content_moderation\Traits\ContentModerationTestTrait;
 use Drupal\user\Entity\Role;
 use Drupal\user\EntityOwnerInterface;
 use Drupal\user\RoleInterface;
@@ -2801,7 +2801,10 @@ abstract class ResourceTestBase extends BrowserTestBase {
     $this->assertTrue($this->container->get('module_installer')->install(['content_moderation'], TRUE), 'Installed modules.');
 
     // Set up an editorial workflow.
-    $workflow = $this->createEditorialWorkflow();
+    $workflow = floatval(\Drupal::VERSION) > 8.5
+      ? $this->createEditorialWorkflow()
+      // @todo Remove when we stop supporting Drupal 8.5.
+      : entity_load('workflow', 'editorial');
     $workflow->getTypePlugin()->addEntityTypeAndBundle(static::$entityTypeId, $this->entity->bundle());
     $workflow->save();