--- /dev/null
+<?php
+
+namespace Drupal\Tests\block\Kernel;
+
+use Drupal\Core\Block\BlockPluginInterface;
+use Drupal\Core\Form\FormState;
+use Drupal\KernelTests\KernelTestBase;
+
+/**
+ * Tests that the block plugin can work properly without a supporting entity.
+ *
+ * @group block
+ */
+class BlockInterfaceTest extends KernelTestBase {
+
+ public static $modules = ['system', 'block', 'block_test', 'user'];
+
+ /**
+ * Test configuration and subsequent form() and build() method calls.
+ *
+ * This test is attempting to test the existing block plugin api and all
+ * functionality that is expected to remain consistent. The arrays that are
+ * used for comparison can change, but only to include elements that are
+ * contained within BlockBase or the plugin being tested. Likely these
+ * comparison arrays should get smaller, not larger, as more form/build
+ * elements are moved into a more suitably responsible class.
+ *
+ * Instantiation of the plugin is the primary element being tested here. The
+ * subsequent method calls are just attempting to cause a failure if a
+ * dependency outside of the plugin configuration is required.
+ */
+ public function testBlockInterface() {
+ $manager = $this->container->get('plugin.manager.block');
+ $configuration = [
+ 'label' => 'Custom Display Message',
+ ];
+ $expected_configuration = [
+ 'id' => 'test_block_instantiation',
+ 'label' => 'Custom Display Message',
+ 'provider' => 'block_test',
+ 'label_display' => BlockPluginInterface::BLOCK_LABEL_VISIBLE,
+ 'display_message' => 'no message set',
+ ];
+ // Initial configuration of the block at construction time.
+ /** @var $display_block \Drupal\Core\Block\BlockPluginInterface */
+ $display_block = $manager->createInstance('test_block_instantiation', $configuration);
+ $this->assertIdentical($display_block->getConfiguration(), $expected_configuration, 'The block was configured correctly.');
+
+ // Updating an element of the configuration.
+ $display_block->setConfigurationValue('display_message', 'My custom display message.');
+ $expected_configuration['display_message'] = 'My custom display message.';
+ $this->assertIdentical($display_block->getConfiguration(), $expected_configuration, 'The block configuration was updated correctly.');
+ $definition = $display_block->getPluginDefinition();
+
+ $expected_form = [
+ 'provider' => [
+ '#type' => 'value',
+ '#value' => 'block_test',
+ ],
+ 'admin_label' => [
+ '#type' => 'item',
+ '#title' => t('Block description'),
+ '#plain_text' => $definition['admin_label'],
+ ],
+ 'label' => [
+ '#type' => 'textfield',
+ '#title' => 'Title',
+ '#maxlength' => 255,
+ '#default_value' => 'Custom Display Message',
+ '#required' => TRUE,
+ ],
+ 'label_display' => [
+ '#type' => 'checkbox',
+ '#title' => 'Display title',
+ '#default_value' => TRUE,
+ '#return_value' => 'visible',
+ ],
+ 'context_mapping' => [],
+ 'display_message' => [
+ '#type' => 'textfield',
+ '#title' => t('Display message'),
+ '#default_value' => 'My custom display message.',
+ ],
+ ];
+ $form_state = new FormState();
+ // Ensure there are no form elements that do not belong to the plugin.
+ $actual_form = $display_block->buildConfigurationForm([], $form_state);
+ // Remove the visibility sections, as that just tests condition plugins.
+ unset($actual_form['visibility'], $actual_form['visibility_tabs']);
+ $this->assertIdentical($this->castSafeStrings($actual_form), $this->castSafeStrings($expected_form), 'Only the expected form elements were present.');
+
+ $expected_build = [
+ '#children' => 'My custom display message.',
+ ];
+ // Ensure the build array is proper.
+ $this->assertIdentical($display_block->build(), $expected_build, 'The plugin returned the appropriate build array.');
+
+ // Ensure the machine name suggestion is correct. In truth, this is actually
+ // testing BlockBase's implementation, not the interface itself.
+ $this->assertIdentical($display_block->getMachineNameSuggestion(), 'displaymessage', 'The plugin returned the expected machine name suggestion.');
+ }
+
+}