.../block/tests/src/Functional/BlockTest.php       |  3 ++-
 .../block_content_test/block_content_test.install  | 29 ++++++++++++++++++++++
 .../src/Functional/BlockContentCreationTest.php    |  8 +++---
 3 files changed, 36 insertions(+), 4 deletions(-)

diff --git a/core/modules/block/tests/src/Functional/BlockTest.php b/core/modules/block/tests/src/Functional/BlockTest.php
index bc6fcded6f..60a43bfbbd 100644
--- a/core/modules/block/tests/src/Functional/BlockTest.php
+++ b/core/modules/block/tests/src/Functional/BlockTest.php
@@ -580,6 +580,7 @@ public function testBlockUserRoleDelete() {
     $block = Block::create([
       'id' => $this->randomMachineName(),
       'plugin' => 'system_powered_by_block',
+      'theme' => 'stark',
     ]);
 
     $block->setVisibilityConfig('user_role', [
@@ -615,7 +616,7 @@ public function testBlockTitle() {
     ];
     // Set the block to be shown only to authenticated users.
     $edit['visibility[user_role][roles][' . RoleInterface::AUTHENTICATED_ID . ']'] = TRUE;
-    $this->drupalGet('admin/structure/block/add/foo/' . $default_theme);
+    $this->drupalGet('admin/structure/block/add/system_powered_by_block/' . $default_theme);
     $this->submitForm($edit, 'Save block');
 
     // Ensure that the title is displayed as plain text.
diff --git a/core/modules/block_content/tests/modules/block_content_test/block_content_test.install b/core/modules/block_content/tests/modules/block_content_test/block_content_test.install
new file mode 100644
index 0000000000..06d47a9645
--- /dev/null
+++ b/core/modules/block_content/tests/modules/block_content_test/block_content_test.install
@@ -0,0 +1,29 @@
+<?php
+
+/**
+ * @file
+ * Install, update and uninstall functions for the block_content_test module.
+ */
+
+use Drupal\block_content\Entity\BlockContent;
+use Drupal\block_content\Entity\BlockContentType;
+
+/**
+ * Implements hook_module_preinstall().
+ */
+function block_content_test_module_preinstall($module) {
+  if ($module === 'block_content_test' && !\Drupal::service('config.installer')->isSyncing()) {
+    // Run before importing config so blocks are created with the correct
+    // dependencies.
+    BlockContentType::create([
+      'id' => 'test',
+      'label' => 'Test',
+    ])->save();
+    BlockContent::create([
+      'type' => 'test',
+      // @see config/install/block.block.foobargorilla.yml
+      'uuid' => 'fb5e8434-3617-4a1d-a252-8273e95ec30e',
+      'info' => 'Something',
+    ])->save();
+  }
+}
diff --git a/core/modules/block_content/tests/src/Functional/BlockContentCreationTest.php b/core/modules/block_content/tests/src/Functional/BlockContentCreationTest.php
index bd499aa22b..5d3f7febdf 100644
--- a/core/modules/block_content/tests/src/Functional/BlockContentCreationTest.php
+++ b/core/modules/block_content/tests/src/Functional/BlockContentCreationTest.php
@@ -205,17 +205,19 @@ public function testBlockDelete() {
     $this->submitForm($edit, 'Save');
 
     // Place the block.
+    // Note: this is the second block_content entity, the first was created in
+    // block_content_test_module_preinstall().
     $instance = [
       'id' => mb_strtolower($edit['info[0][value]']),
       'settings[label]' => $edit['info[0][value]'],
       'region' => 'sidebar_first',
     ];
-    $block = BlockContent::load(1);
+    $block = BlockContent::load(2);
     $url = 'admin/structure/block/add/block_content:' . $block->uuid() . '/' . $this->config('system.theme')->get('default');
     $this->drupalGet($url);
     $this->submitForm($instance, 'Save block');
 
-    $block = BlockContent::load(1);
+    $block = BlockContent::load(2);
 
     // Test getInstances method.
     $this->assertCount(1, $block->getInstances());
@@ -225,7 +227,7 @@ public function testBlockDelete() {
     $this->assertSession()->pageTextContains($body);
 
     // Delete the block.
-    $this->drupalGet('admin/content/block/1/delete');
+    $this->drupalGet('admin/content/block/2/delete');
     $this->assertSession()->pageTextContains('This will also remove 1 placed block instance.');
 
     $this->submitForm([], 'Delete');