Issue #3046297 by eiriksm: Add some tests

tests/src/FunctionalJavascript/WidgetAdminTest.php

+<?php
+
+namespace Drupal\Tests\image_canvas_editor_api\FunctionalJavascript;
+
+use Drupal\Tests\image\FunctionalJavascript\ImageFieldTestBase;
+
+/**
+ * @group image_canvas_editor_api
+ */
+class WidgetAdminTest extends ImageFieldTestBase {
+
+  /**
+   * Modules to enable.
+   *
+   * @var array
+   */
+  public static $modules = [
+    'node',
+    'image',
+    'field_ui',
+    'image_canvas_editor_api',
+  ];
+
+  protected function setUp() {
+    parent::setUp();
+
+    $web_user = $this->drupalCreateUser(['bypass node access', 'administer content types', 'administer node fields', 'administer node form display', 'administer node display']);
+    $this->drupalLogin($web_user);
+  }
+
+  /**
+   * Test the fact that we can select image canvas editor as widget.
+   */
+  public function testAdminWidget() {
+    $field_name = strtolower($this->randomMachineName());
+    $this->createImageField($field_name, 'article', ['cardinality' => -1]);
+    $this->drupalGet('admin/structure/types/manage/article/form-display');
+    $this->getSession()->getPage()->selectFieldOption("fields[$field_name][type]", 'image_canvas_editor');
+  }
+
+}