diff --git a/core/modules/aggregator/src/Plugin/Block/AggregatorFeedBlock.php b/core/modules/aggregator/src/Plugin/Block/AggregatorFeedBlock.php
index 90d8f669dda51d056b910da75b16d4cd0260009b..f4c8e2a57d18c526fc44a7e15a68863f94e6fd18 100644
--- a/core/modules/aggregator/src/Plugin/Block/AggregatorFeedBlock.php
+++ b/core/modules/aggregator/src/Plugin/Block/AggregatorFeedBlock.php
@@ -167,8 +167,10 @@ public function build() {
    */
   public function getCacheTags() {
     $cache_tags = parent::getCacheTags();
-    $feed = $this->feedStorage->load($this->configuration['feed']);
-    return Cache::mergeTags($cache_tags, $feed->getCacheTags());
+    if ($feed = $this->feedStorage->load($this->configuration['feed'])) {
+      $cache_tags = Cache::mergeTags($cache_tags, $feed->getCacheTags());
+    }
+    return $cache_tags;
   }
 
 }
diff --git a/core/modules/migrate_drupal/tests/src/Kernel/d6/MigrateDrupal6AuditIdsTest.php b/core/modules/migrate_drupal/tests/src/Kernel/d6/MigrateDrupal6AuditIdsTest.php
index a0bb591c4c85cefddf060607720cd474b6037121..860f5768dd126da6ac3410ffd4e0d74f4fa72492 100644
--- a/core/modules/migrate_drupal/tests/src/Kernel/d6/MigrateDrupal6AuditIdsTest.php
+++ b/core/modules/migrate_drupal/tests/src/Kernel/d6/MigrateDrupal6AuditIdsTest.php
@@ -37,6 +37,7 @@ protected function setUp() {
     $this->installSchema('forum', ['forum_index']);
     $this->installSchema('node', ['node_access']);
     $this->installSchema('search', ['search_dataset']);
+    $this->installSchema('system', ['sequences']);
     $this->installSchema('tracker', ['tracker_node', 'tracker_user']);
 
     // Enable content moderation for nodes of type page.
diff --git a/core/modules/migrate_drupal/tests/src/Kernel/d7/MigrateDrupal7AuditIdsTest.php b/core/modules/migrate_drupal/tests/src/Kernel/d7/MigrateDrupal7AuditIdsTest.php
index 1d7442383825f6c472c762f0ce70e7cee795433c..351ab43d7261fab6491f1992f1797f3f6501ba8a 100644
--- a/core/modules/migrate_drupal/tests/src/Kernel/d7/MigrateDrupal7AuditIdsTest.php
+++ b/core/modules/migrate_drupal/tests/src/Kernel/d7/MigrateDrupal7AuditIdsTest.php
@@ -37,6 +37,7 @@ protected function setUp() {
     $this->installSchema('forum', ['forum_index']);
     $this->installSchema('node', ['node_access']);
     $this->installSchema('search', ['search_dataset']);
+    $this->installSchema('system', ['sequences']);
     $this->installSchema('tracker', ['tracker_node', 'tracker_user']);
 
     // Enable content moderation for nodes of type page.
diff --git a/core/modules/migrate_drupal/tests/src/Traits/CreateTestContentEntitiesTrait.php b/core/modules/migrate_drupal/tests/src/Traits/CreateTestContentEntitiesTrait.php
index db720e8cb7863eb47fab5de481934adec6e345a5..8896222f93f494acbe5bd0b39c67a4421eb6cc34 100644
--- a/core/modules/migrate_drupal/tests/src/Traits/CreateTestContentEntitiesTrait.php
+++ b/core/modules/migrate_drupal/tests/src/Traits/CreateTestContentEntitiesTrait.php
@@ -2,16 +2,6 @@
 
 namespace Drupal\Tests\migrate_drupal\Traits;
 
-use Drupal\aggregator\Entity\Feed;
-use Drupal\aggregator\Entity\Item;
-use Drupal\block_content\Entity\BlockContent;
-use Drupal\comment\Entity\Comment;
-use Drupal\file\Entity\File;
-use Drupal\menu_link_content\Entity\MenuLinkContent;
-use Drupal\node\Entity\Node;
-use Drupal\taxonomy\Entity\Term;
-use Drupal\user\Entity\User;
-
 /**
  * Provides helper methods for creating test content.
  */
@@ -60,72 +50,161 @@ protected function installEntitySchemas() {
    * Create several pieces of generic content.
    */
   protected function createContent() {
+    $entity_type_manager = \Drupal::entityTypeManager();
+
     // Create an aggregator feed.
-    $feed = Feed::create([
-      'title' => 'feed',
-      'url' => 'http://www.example.com',
-    ]);
-    $feed->save();
-
-    // Create an aggregator feed item.
-    $item = Item::create([
-      'title' => 'feed item',
-      'fid' => $feed->id(),
-      'link' => 'http://www.example.com',
-    ]);
-    $item->save();
+    if ($entity_type_manager->hasDefinition('aggregator_feed')) {
+      $feed = $entity_type_manager->getStorage('aggregator_feed')->create([
+        'title' => 'feed',
+        'url' => 'http://www.example.com',
+      ]);
+      $feed->save();
+
+      // Create an aggregator feed item.
+      $item = $entity_type_manager->getStorage('aggregator_item')->create([
+        'title' => 'feed item',
+        'fid' => $feed->id(),
+        'link' => 'http://www.example.com',
+      ]);
+      $item->save();
+    }
+
+    // Create a block content.
+    if ($entity_type_manager->hasDefinition('block_content')) {
+      $block = $entity_type_manager->getStorage('block_content')->create([
+        'info' => 'block',
+        'type' => 'block',
+      ]);
+      $block->save();
+    }
+
+    // Create a node.
+    if ($entity_type_manager->hasDefinition('node')) {
+      $node = $entity_type_manager->getStorage('node')->create([
+        'type' => 'page',
+        'title' => 'page',
+      ]);
+      $node->save();
+
+      // Create a comment.
+      if ($entity_type_manager->hasDefinition('comment')) {
+        $comment = $entity_type_manager->getStorage('comment')->create([
+          'comment_type' => 'comment',
+          'field_name' => 'comment',
+          'entity_type' => 'node',
+          'entity_id' => $node->id(),
+        ]);
+        $comment->save();
+      }
+    }
+
+    // Create a file.
+    if ($entity_type_manager->hasDefinition('file')) {
+      $file = $entity_type_manager->getStorage('file')->create([
+        'uri' => 'public://example.txt',
+      ]);
+      $file->save();
+    }
+
+    // Create a menu link.
+    if ($entity_type_manager->hasDefinition('menu_link_content')) {
+      $menu_link = $entity_type_manager->getStorage('menu_link_content')->create([
+        'title' => 'menu link',
+        'link' => ['uri' => 'http://www.example.com'],
+        'menu_name' => 'tools',
+      ]);
+      $menu_link->save();
+    }
+
+    // Create a taxonomy term.
+    if ($entity_type_manager->hasDefinition('taxonomy_term')) {
+      $term = $entity_type_manager->getStorage('taxonomy_term')->create([
+        'name' => 'term',
+        'vid' => 'term',
+      ]);
+      $term->save();
+    }
+
+    // Create a user.
+    if ($entity_type_manager->hasDefinition('user')) {
+      $user = $entity_type_manager->getStorage('user')->create([
+        'name' => 'user',
+        'mail' => 'user@example.com',
+      ]);
+      $user->save();
+    }
+  }
+
+  /**
+   * Create several pieces of generic content.
+   */
+  protected function createContentPostUpgrade() {
+    $entity_type_manager = \Drupal::entityTypeManager();
 
     // Create a block content.
-    $block = BlockContent::create([
-      'info' => 'block',
-      'type' => 'block',
-    ]);
-    $block->save();
+    if ($entity_type_manager->hasDefinition('block_content')) {
+      $block = $entity_type_manager->getStorage('block_content')->create([
+        'info' => 'Post upgrade block',
+        'type' => 'block',
+      ]);
+      $block->save();
+    }
 
     // Create a node.
-    $node = Node::create([
-      'type' => 'page',
-      'title' => 'page',
-    ]);
-    $node->save();
-
-    // Create a comment.
-    $comment = Comment::create([
-      'comment_type' => 'comment',
-      'field_name' => 'comment',
-      'entity_type' => 'node',
-      'entity_id' => $node->id(),
-    ]);
-    $comment->save();
+    if ($entity_type_manager->hasDefinition('node')) {
+      $node = $entity_type_manager->getStorage('node')->create([
+        'type' => 'page',
+        'title' => 'Post upgrade page',
+      ]);
+      $node->save();
+
+      // Create a comment.
+      if ($entity_type_manager->hasDefinition('comment')) {
+        $comment = $entity_type_manager->getStorage('comment')->create([
+          'comment_type' => 'comment',
+          'field_name' => 'comment',
+          'entity_type' => 'node',
+          'entity_id' => $node->id(),
+        ]);
+        $comment->save();
+      }
+    }
 
     // Create a file.
-    $file = File::create([
-      'uri' => 'public://example.txt',
-    ]);
-    $file->save();
+    if ($entity_type_manager->hasDefinition('file')) {
+      $file = $entity_type_manager->getStorage('file')->create([
+        'uri' => 'public://post_upgrade_example.txt',
+      ]);
+      $file->save();
+    }
 
     // Create a menu link.
-    $menu_link = MenuLinkContent::create([
-      'title' => 'menu link',
-      'link' => ['uri' => 'http://www.example.com'],
-      'menu_name' => 'tools',
-    ]);
-    $menu_link->save();
+    if ($entity_type_manager->hasDefinition('menu_link_content')) {
+      $menu_link = $entity_type_manager->getStorage('menu_link_content')->create([
+        'title' => 'post upgrade menu link',
+        'link' => ['uri' => 'http://www.drupal.org'],
+        'menu_name' => 'tools',
+      ]);
+      $menu_link->save();
+    }
 
     // Create a taxonomy term.
-    $term = Term::create([
-      'name' => 'term',
-      'vid' => 'term',
-    ]);
-    $term->save();
+    if ($entity_type_manager->hasDefinition('taxonomy_term')) {
+      $term = $entity_type_manager->getStorage('taxonomy_term')->create([
+        'name' => 'post upgrade term',
+        'vid' => 'term',
+      ]);
+      $term->save();
+    }
 
     // Create a user.
-    $user = User::create([
-      'uid' => 2,
-      'name' => 'user',
-      'mail' => 'user@example.com',
-    ]);
-    $user->save();
+    if ($entity_type_manager->hasDefinition('user')) {
+      $user = $entity_type_manager->getStorage('user')->create([
+        'name' => 'universe',
+        'mail' => 'universe@example.com',
+      ]);
+      $user->save();
+    }
   }
 
 }
diff --git a/core/modules/migrate_drupal_ui/migrate_drupal_ui.module b/core/modules/migrate_drupal_ui/migrate_drupal_ui.module
index 0a8471add805999e0f5b406a987022b28dde76cf..aef9f9138b61e0d6094e67a18d5d49e0fa676407 100644
--- a/core/modules/migrate_drupal_ui/migrate_drupal_ui.module
+++ b/core/modules/migrate_drupal_ui/migrate_drupal_ui.module
@@ -31,8 +31,6 @@ function migrate_drupal_ui_help($route_name, RouteMatchInterface $route_match) {
       $output .= '<dt>' . t('Reviewing the upgrade log') . '</dt>';
       $output .= '<dd>' . t('You can review a <a href=":log">log of upgrade messages</a> by clicking the link in the message provided after the upgrade or by filtering the messages for the type <em>migrate_drupal_ui</em> on the <a href=":messages">Recent log messages</a> page.',
           [':log' => \Drupal::url('migrate_drupal_ui.log'), ':messages' => \Drupal::url('dblog.overview')]) . '</dd>';
-      $output .= '<dt>' . t('Incremental upgrades') . '</dt>';
-      $output .= '<dd>' . t('Incremental upgrades are not yet supported through the user interface.') . '</dd>';
       $output .= '<dt>' . t('Rolling back an upgrade') . '</dt>';
       $output .= '<dd>' . t('Rolling back an upgrade is not yet supported through the user interface.') . '</dd>';
       $output .= '</dl>';
diff --git a/core/modules/migrate_drupal_ui/src/Form/MigrateUpgradeForm.php b/core/modules/migrate_drupal_ui/src/Form/MigrateUpgradeForm.php
index c080a3917fc808e9798caf974eb845985e18bc92..59f28a63bb1f5666a21ef84b37cf0b36227b8d29 100644
--- a/core/modules/migrate_drupal_ui/src/Form/MigrateUpgradeForm.php
+++ b/core/modules/migrate_drupal_ui/src/Form/MigrateUpgradeForm.php
@@ -2,6 +2,7 @@
 
 namespace Drupal\migrate_drupal_ui\Form;
 
+use Drupal\Core\Database\DatabaseExceptionWrapper;
 use Drupal\Core\Datetime\DateFormatterInterface;
 use Drupal\Core\Extension\ModuleHandlerInterface;
 use Drupal\Core\Form\ConfirmFormBase;
@@ -279,9 +280,16 @@ public function buildOverviewForm(array $form, FormStateInterface $form_state) {
       //   https://www.drupal.org/node/2687849
       $form['upgrade_option_item'] = [
         '#type' => 'item',
-        '#prefix' => $this->t('An upgrade has already been performed on this site. To perform a new migration, create a clean and empty new install of Drupal 8. Rollbacks and incremental migrations are not yet supported through the user interface. For more information, see the <a href=":url">upgrading handbook</a>.', [':url' => 'https://www.drupal.org/upgrade/migrate']),
+        '#prefix' => $this->t('An upgrade has already been performed on this site. To perform a new migration, create a clean and empty new install of Drupal 8. Rollbacks are not yet supported through the user interface. For more information, see the <a href=":url">upgrading handbook</a>.', [':url' => 'https://www.drupal.org/upgrade/migrate']),
         '#description' => $this->t('Last upgrade: @date', ['@date' => $this->dateFormatter->format($date_performed)]),
       ];
+      $form['actions']['incremental'] = [
+        '#type' => 'submit',
+        '#value' => $this->t('Import new configuration and content from old site'),
+        '#button_type' => 'primary',
+        '#validate' => ['::validateIncrementalForm'],
+        '#submit' => ['::submitIncrementalForm'],
+      ];
       return $form;
     }
     else {
@@ -344,8 +352,50 @@ public function buildOverviewForm(array $form, FormStateInterface $form_state) {
    *   The current state of the form.
    */
   public function submitOverviewForm(array &$form, FormStateInterface $form_state) {
-    $form_state->set('step', 'credentials');
-    $form_state->setRebuild();
+    $form_state->set('step', 'credentials')->setRebuild();
+  }
+
+  /**
+   * Validation handler for the incremental overview form.
+   *
+   * @param array $form
+   *   An associative array containing the structure of the form.
+   * @param \Drupal\Core\Form\FormStateInterface $form_state
+   *   The current state of the form.
+   */
+  public function validateIncrementalForm(array &$form, FormStateInterface $form_state) {
+    // Retrieve the database driver from state.
+    $database_state_key = $this->state->get('migrate.fallback_state_key', '');
+    if ($database_state_key) {
+      try {
+        $database = $this->state->get($database_state_key, [])['database'];
+        if ($connection = $this->getConnection($database)) {
+          if ($version = $this->getLegacyDrupalVersion($connection)) {
+            $this->setupMigrations($database, $form_state);
+            $valid_legacy_database = TRUE;
+          }
+        }
+      }
+      catch (DatabaseExceptionWrapper $exception) {
+        // Hide DB exceptions and forward to the DB credentials form. In that
+        // form we can more properly display errors and accept new credentials.
+      }
+    }
+    if (empty($valid_legacy_database)) {
+      $form_state->setValue('step', 'credentials')->setRebuild();
+    }
+  }
+
+  /**
+   * Form submission handler for the incremental overview form.
+   *
+   * @param array $form
+   *   An associative array containing the structure of the form.
+   * @param \Drupal\Core\Form\FormStateInterface $form_state
+   *   The current state of the form.
+   */
+  public function submitIncrementalForm(array &$form, FormStateInterface $form_state) {
+    $form_state->set('step', 'confirm_id_conflicts')->setRebuild();
   }
 
   /**
@@ -528,31 +578,7 @@ public function validateCredentialForm(array &$form, FormStateInterface $form_st
         ]));
       }
       else {
-        $this->createDatabaseStateSettings($database, $version);
-        $migrations = $this->getMigrations('migrate_drupal_' . $version, $version);
-
-        // Get the system data from source database.
-        $system_data = $this->getSystemData($connection);
-
-        // Convert the migration object into array
-        // so that it can be stored in form storage.
-        $migration_array = [];
-        foreach ($migrations as $migration) {
-          $migration_array[$migration->id()] = $migration->label();
-        }
-
-        // Store the retrieved migration IDs in form storage.
-        $form_state->set('version', $version);
-        $form_state->set('migrations', $migration_array);
-        if ($version === '6') {
-          $form_state->set('source_base_path', $form_state->getValue('d6_source_base_path'));
-        }
-        else {
-          $form_state->set('source_base_path', $form_state->getValue('source_base_path'));
-        }
-        $form_state->set('source_private_file_path', $form_state->getValue('source_private_file_path'));
-        // Store the retrived system data in form storage.
-        $form_state->set('system_data', $system_data);
+        $this->setupMigrations($database, $form_state);
       }
     }
     catch (\Exception $e) {
@@ -974,6 +1000,48 @@ protected function getDatabaseTypes() {
     return drupal_get_database_types();
   }
 
+  /**
+   * Puts migrations information in form state.
+   *
+   * Gets all the migrations, converts each to an array and stores it in the
+   * form state. The source base path for public and private files is also
+   * put into form state.
+   *
+   * @param array $database
+   *   Database array representing the source Drupal database.
+   * @param \Drupal\Core\Form\FormStateInterface $form_state
+   *   The current state of the form.
+   */
+  protected function setupMigrations(array $database, FormStateInterface $form_state) {
+    $connection = $this->getConnection($database);
+    $version = $this->getLegacyDrupalVersion($connection);
+    $this->createDatabaseStateSettings($database, $version);
+    $migrations = $this->getMigrations('migrate_drupal_' . $version, $version);
+
+    // Get the system data from source database.
+    $system_data = $this->getSystemData($connection);
+
+    // Convert the migration object into array
+    // so that it can be stored in form storage.
+    $migration_array = [];
+    foreach ($migrations as $migration) {
+      $migration_array[$migration->id()] = $migration->label();
+    }
+
+    // Store the retrieved migration IDs in form storage.
+    $form_state->set('version', $version);
+    $form_state->set('migrations', $migration_array);
+    if ($version == 6) {
+      $form_state->set('source_base_path', $form_state->getValue('d6_source_base_path'));
+    }
+    else {
+      $form_state->set('source_base_path', $form_state->getValue('source_base_path'));
+    }
+    $form_state->set('source_private_file_path', $form_state->getValue('source_private_file_path'));
+    // Store the retrieved system data in form storage.
+    $form_state->set('system_data', $system_data);
+  }
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/migrate_drupal_ui/tests/src/Functional/MigrateUpgradeExecuteTestBase.php b/core/modules/migrate_drupal_ui/tests/src/Functional/MigrateUpgradeExecuteTestBase.php
index 4758a5e34382b9957afef76d5cee2ce5dea6795e..a9d7de1089e5551991e75551286e19d80e738003 100644
--- a/core/modules/migrate_drupal_ui/tests/src/Functional/MigrateUpgradeExecuteTestBase.php
+++ b/core/modules/migrate_drupal_ui/tests/src/Functional/MigrateUpgradeExecuteTestBase.php
@@ -2,7 +2,6 @@
 
 namespace Drupal\Tests\migrate_drupal_ui\Functional;
 
-use Drupal\migrate\Plugin\MigrateIdMapInterface;
 use Drupal\migrate_drupal\MigrationConfigurationTrait;
 use Drupal\Tests\migrate_drupal\Traits\CreateTestContentEntitiesTrait;
 
@@ -26,6 +25,12 @@ protected function setUp() {
 
   /**
    * Executes all steps of migrations upgrade.
+   *
+   * The upgrade is started three times. The first time is to test that
+   * providing incorrect database credentials fails as expected. The second
+   * time is to run the migration and assert the results. The third time is
+   * to test an incremental migration, by installing the aggregator module,
+   * and assert the results.
    */
   public function testMigrateUpgradeExecute() {
     $connection_options = $this->sourceDatabase->getConnectionOptions();
@@ -84,22 +89,11 @@ public function testMigrateUpgradeExecute() {
     $session->fieldExists('mysql[host]');
 
     $this->drupalPostForm(NULL, $edits, t('Review upgrade'));
-    $session->pageTextContains('WARNING: Content may be overwritten on your new site.');
-    $session->pageTextContains('There is conflicting content of these types:');
-    $session->pageTextContains('aggregator feed entities');
-    $session->pageTextContains('aggregator feed item entities');
-    $session->pageTextContains('custom block entities');
-    $session->pageTextContains('custom menu link entities');
-    $session->pageTextContains('file entities');
-    $session->pageTextContains('taxonomy term entities');
-    $session->pageTextContains('user entities');
-    $session->pageTextContains('comments');
-    $session->pageTextContains('content item revisions');
-    $session->pageTextContains('content items');
-    $session->pageTextContains('There is translated content of these types:');
+    $this->assertIdConflict($session);
+
     $this->drupalPostForm(NULL, [], t('I acknowledge I may lose data. Continue anyway.'));
     $session->statusCodeEquals(200);
-    $session->pageTextContains('What will be upgraded?');
+
     // Ensure there are no errors about missing modules from the test module.
     $session->pageTextNotContains(t('Source module not found for migration_provider_no_annotation.'));
     $session->pageTextNotContains(t('Source module not found for migration_provider_test.'));
@@ -109,49 +103,40 @@ public function testMigrateUpgradeExecute() {
     // Test the upgrade paths.
     $available_paths = $this->getAvailablePaths();
     $missing_paths = $this->getMissingPaths();
-    $this->assertUpgradePaths($session, $available_paths, $missing_paths);
+    $this->assertReviewPage($session, $available_paths, $missing_paths);
 
     $this->drupalPostForm(NULL, [], t('Perform upgrade'));
     $this->assertText(t('Congratulations, you upgraded Drupal!'));
+    $this->assertMigrationResults($this->getEntityCounts(), $version);
 
-    // Have to reset all the statics after migration to ensure entities are
-    // loadable.
-    $this->resetAll();
-
-    $expected_counts = $this->getEntityCounts();
-    foreach (array_keys(\Drupal::entityTypeManager()
-      ->getDefinitions()) as $entity_type) {
-      $real_count = \Drupal::entityQuery($entity_type)->count()->execute();
-      $expected_count = isset($expected_counts[$entity_type]) ? $expected_counts[$entity_type] : 0;
-      $this->assertEqual($expected_count, $real_count, "Found $real_count $entity_type entities, expected $expected_count.");
-    }
-
-    $plugin_manager = \Drupal::service('plugin.manager.migration');
-    /** @var \Drupal\migrate\Plugin\Migration[] $all_migrations */
-    $all_migrations = $plugin_manager->createInstancesByTag('Drupal ' . $version);
-    foreach ($all_migrations as $migration) {
-      $id_map = $migration->getIdMap();
-      foreach ($id_map as $source_id => $map) {
-        // Convert $source_id into a keyless array so that
-        // \Drupal\migrate\Plugin\migrate\id_map\Sql::getSourceHash() works as
-        // expected.
-        $source_id_values = array_values(unserialize($source_id));
-        $row = $id_map->getRowBySource($source_id_values);
-        $destination = serialize($id_map->currentDestination());
-        $message = "Migration of $source_id to $destination as part of the {$migration->id()} migration. The source row status is " . $row['source_row_status'];
-        // A completed migration should have maps with
-        // MigrateIdMapInterface::STATUS_IGNORED or
-        // MigrateIdMapInterface::STATUS_IMPORTED.
-        if ($row['source_row_status'] == MigrateIdMapInterface::STATUS_FAILED || $row['source_row_status'] == MigrateIdMapInterface::STATUS_NEEDS_UPDATE) {
-          $this->fail($message);
-        }
-        else {
-          $this->pass($message);
-        }
-      }
-    }
     \Drupal::service('module_installer')->install(['forum']);
     \Drupal::service('module_installer')->install(['book']);
+
+    // Test incremental migration.
+    $this->createContentPostUpgrade();
+
+    $this->drupalGet('/upgrade');
+    $session->pageTextContains('An upgrade has already been performed on this site. To perform a new migration, create a clean and empty new install of Drupal 8. Rollbacks are not yet supported through the user interface.');
+    $this->drupalPostForm(NULL, [], t('Import new configuration and content from old site'));
+    $session->pageTextContains('WARNING: Content may be overwritten on your new site.');
+    $session->pageTextContains('There is conflicting content of these types:');
+    $session->pageTextContains('file entities');
+    $session->pageTextContains('content item revisions');
+    $session->pageTextContains('There is translated content of these types:');
+    $session->pageTextContains('content items');
+
+    $this->drupalPostForm(NULL, [], t('I acknowledge I may lose data. Continue anyway.'));
+    $session->statusCodeEquals(200);
+
+    // Need to update available and missing path lists.
+    $all_available = $this->getAvailablePaths();
+    $all_available[] = 'aggregator';
+    $all_missing = $this->getMissingPaths();
+    $all_missing = array_diff($all_missing, ['aggregator']);
+    $this->assertReviewPage($session, $all_available, $all_missing);
+    $this->drupalPostForm(NULL, [], t('Perform upgrade'));
+    $session->pageTextContains(t('Congratulations, you upgraded Drupal!'));
+    $this->assertMigrationResults($this->getEntityCountsIncremental(), $version);
   }
 
 }
diff --git a/core/modules/migrate_drupal_ui/tests/src/Functional/MigrateUpgradeReviewPageTestBase.php b/core/modules/migrate_drupal_ui/tests/src/Functional/MigrateUpgradeReviewPageTestBase.php
index eb72bdd12a51035a11ee6c374ce2beeecf211b77..4138bea5b5b6acabf6da49126284d3eeab7b3aef 100644
--- a/core/modules/migrate_drupal_ui/tests/src/Functional/MigrateUpgradeReviewPageTestBase.php
+++ b/core/modules/migrate_drupal_ui/tests/src/Functional/MigrateUpgradeReviewPageTestBase.php
@@ -121,4 +121,11 @@ protected function getEntityCounts() {
     return [];
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  protected function getEntityCountsIncremental() {
+    return [];
+  }
+
 }
diff --git a/core/modules/migrate_drupal_ui/tests/src/Functional/MigrateUpgradeTestBase.php b/core/modules/migrate_drupal_ui/tests/src/Functional/MigrateUpgradeTestBase.php
index 624a0525592263811f2c542aedc02793727ba072..23d5c295f3c6eed43fef5d0e8799f5939e3f6b96 100644
--- a/core/modules/migrate_drupal_ui/tests/src/Functional/MigrateUpgradeTestBase.php
+++ b/core/modules/migrate_drupal_ui/tests/src/Functional/MigrateUpgradeTestBase.php
@@ -3,6 +3,7 @@
 namespace Drupal\Tests\migrate_drupal_ui\Functional;
 
 use Drupal\Core\Database\Database;
+use Drupal\migrate\Plugin\MigrateIdMapInterface;
 use Drupal\migrate_drupal\MigrationConfigurationTrait;
 use Drupal\Tests\BrowserTestBase;
 use Drupal\Tests\migrate_drupal\Traits\CreateTestContentEntitiesTrait;
@@ -178,4 +179,107 @@ abstract protected function getAvailablePaths();
    */
   abstract protected function getMissingPaths();
 
+  /**
+   * Gets expected number of entities per entity after incremental migration.
+   *
+   * @return int[]
+   *   An array of expected counts keyed by entity type ID.
+   */
+  abstract protected function getEntityCountsIncremental();
+
+  /**
+   * Helper method to assert the text on the 'Upgrade analysis report' page.
+   *
+   * @param \Drupal\Tests\WebAssert $session
+   *   The current session.
+   * @param array $all_available
+   *   Array of modules that will be upgraded.
+   * @param array $all_missing
+   *   Array of modules that will not be upgraded.
+   */
+  protected function assertReviewPage(WebAssert $session, array $all_available, array $all_missing) {
+    $this->assertText('What will be upgraded?');
+
+    // Ensure there are no errors about the missing modules from the test module.
+    $session->pageTextNotContains(t('Source module not found for migration_provider_no_annotation.'));
+    $session->pageTextNotContains(t('Source module not found for migration_provider_test.'));
+    $session->pageTextNotContains(t('Destination module not found for migration_provider_test'));
+    // Ensure there are no errors about any other missing migration providers.
+    $session->pageTextNotContains(t('module not found'));
+
+    // Test the available migration paths.
+    foreach ($all_available as $available) {
+      $session->elementExists('xpath', "//span[contains(@class, 'checked') and text() = '$available']");
+      $session->elementNotExists('xpath', "//span[contains(@class, 'error') and text() = '$available']");
+    }
+
+    // Test the missing migration paths.
+    foreach ($all_missing as $missing) {
+      $session->elementExists('xpath', "//span[contains(@class, 'error') and text() = '$missing']");
+      $session->elementNotExists('xpath', "//span[contains(@class, 'checked') and text() = '$missing']");
+    }
+  }
+
+  /**
+   * Helper method that asserts text on the ID conflict form.
+   *
+   * @param \Drupal\Tests\WebAssert $session
+   *   The current session.
+   * @param $session
+   *   The current session.
+   */
+  protected function assertIdConflict(WebAssert $session) {
+    $session->pageTextContains('WARNING: Content may be overwritten on your new site.');
+    $session->pageTextContains('There is conflicting content of these types:');
+    $session->pageTextContains('custom block entities');
+    $session->pageTextContains('custom menu link entities');
+    $session->pageTextContains('file entities');
+    $session->pageTextContains('taxonomy term entities');
+    $session->pageTextContains('user entities');
+    $session->pageTextContains('comments');
+    $session->pageTextContains('content item revisions');
+    $session->pageTextContains('content items');
+    $session->pageTextContains('There is translated content of these types:');
+  }
+
+  /**
+   * Checks that migrations have been performed successfully.
+   *
+   * @param array $expected_counts
+   *   The expected counts of each entity type.
+   * @param int $version
+   *   The Drupal version.
+   */
+  protected function assertMigrationResults(array $expected_counts, $version) {
+    // Have to reset all the statics after migration to ensure entities are
+    // loadable.
+    $this->resetAll();
+    foreach (array_keys(\Drupal::entityTypeManager()->getDefinitions()) as $entity_type) {
+      $real_count = (int) \Drupal::entityQuery($entity_type)->count()->execute();
+      $expected_count = isset($expected_counts[$entity_type]) ? $expected_counts[$entity_type] : 0;
+      $this->assertSame($expected_count, $real_count, "Found $real_count $entity_type entities, expected $expected_count.");
+    }
+
+    $plugin_manager = \Drupal::service('plugin.manager.migration');
+    /** @var \Drupal\migrate\Plugin\Migration[] $all_migrations */
+    $all_migrations = $plugin_manager->createInstancesByTag('Drupal ' . $version);
+    foreach ($all_migrations as $migration) {
+      $id_map = $migration->getIdMap();
+      foreach ($id_map as $source_id => $map) {
+        // Convert $source_id into a keyless array so that
+        // \Drupal\migrate\Plugin\migrate\id_map\Sql::getSourceHash() works as
+        // expected.
+        $source_id_values = array_values(unserialize($source_id));
+        $row = $id_map->getRowBySource($source_id_values);
+        $destination = serialize($id_map->currentDestination());
+        $message = "Migration of $source_id to $destination as part of the {$migration->id()} migration. The source row status is " . $row['source_row_status'];
+        // A completed migration should have maps with
+        // MigrateIdMapInterface::STATUS_IGNORED or
+        // MigrateIdMapInterface::STATUS_IMPORTED.
+        $this->assertNotSame(MigrateIdMapInterface::STATUS_FAILED, $row['source_row_status'], $message);
+        $this->assertNotSame(MigrateIdMapInterface::STATUS_NEEDS_UPDATE, $row['source_row_status'], $message);
+      }
+    }
+  }
+
 }
diff --git a/core/modules/migrate_drupal_ui/tests/src/Functional/d6/MigrateUpgrade6Test.php b/core/modules/migrate_drupal_ui/tests/src/Functional/d6/MigrateUpgrade6Test.php
index 474a9a9897b27d3859e6f6a2480025e6ccea9c89..71eebe823b92b0815660a2f81a05415de854858a 100644
--- a/core/modules/migrate_drupal_ui/tests/src/Functional/d6/MigrateUpgrade6Test.php
+++ b/core/modules/migrate_drupal_ui/tests/src/Functional/d6/MigrateUpgrade6Test.php
@@ -96,6 +96,24 @@ protected function getEntityCounts() {
     ];
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  protected function getEntityCountsIncremental() {
+    $counts = $this->getEntityCounts();
+    $counts['block_content'] = 3;
+    $counts['comment'] = 7;
+    $counts['entity_view_display'] = 53;
+    $counts['entity_view_mode'] = 14;
+    $counts['file'] = 9;
+    $counts['menu_link_content'] = 6;
+    $counts['node'] = 18;
+    $counts['taxonomy_term'] = 9;
+    $counts['user'] = 8;
+    $counts['view'] = 16;
+    return $counts;
+  }
+
   /**
    * {@inheritdoc}
    */
diff --git a/core/modules/migrate_drupal_ui/tests/src/Functional/d7/MigrateUpgrade7Test.php b/core/modules/migrate_drupal_ui/tests/src/Functional/d7/MigrateUpgrade7Test.php
index 2b31a7990bef608a0f2bd70664f0b35f48832187..385a4e58040a3d95acefd61a9572674ba4be0a2e 100644
--- a/core/modules/migrate_drupal_ui/tests/src/Functional/d7/MigrateUpgrade7Test.php
+++ b/core/modules/migrate_drupal_ui/tests/src/Functional/d7/MigrateUpgrade7Test.php
@@ -96,6 +96,21 @@ protected function getEntityCounts() {
     ];
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  protected function getEntityCountsIncremental() {
+    $counts = $this->getEntityCounts();
+    $counts['block_content'] = 2;
+    $counts['comment'] = 2;
+    $counts['file'] = 4;
+    $counts['menu_link_content'] = 9;
+    $counts['node'] = 6;
+    $counts['taxonomy_term'] = 19;
+    $counts['user'] = 5;
+    return $counts;
+  }
+
   /**
    * {@inheritdoc}
    */