Issue #2991542 by mondrake, voleger: Introduce a DatabaseLegacyTest class for deprecation testing

(cherry picked from commit 3f44f5bb)

core/tests/Drupal/KernelTests/Core/Database/DatabaseLegacyTest.php

+<?php
+
+namespace Drupal\KernelTests\Core\Database;
+
+/**
+ * Deprecation tests cases for the database layer.
+ *
+ * @group legacy
+ */
+class DatabaseLegacyTest extends DatabaseTestBase {
+
+  /**
+   * Tests the db_table_exists() function.
+   *
+   * @expectedDeprecation db_table_exists() is deprecated in Drupal 8.0.x and will be removed before Drupal 9.0.0. Use $injected_database->schema()->tableExists($table) instead. See https://www.drupal.org/node/2947929.
+   */
+  public function testDbTableExists() {
+    $this->assertTrue(db_table_exists('test'));
+  }
+
+  /**
+   * Tests the db_set_active() function.
+   *
+   * @expectedDeprecation db_set_active() is deprecated in Drupal 8.0.x and will be removed before Drupal 9.0.0. Use \Drupal\Core\Database\Database::setActiveConnection() instead. See https://www.drupal.org/node/2944084.
+   */
+  public function testDbSetActive() {
+    $get_active_db = $this->connection->getKey();
+    $this->assert(db_set_active($get_active_db), 'Database connection is active');
+  }
+
+  /**
+   * Tests the db_drop_table() function.
+   *
+   * @expectedDeprecation db_drop_table() is deprecated in Drupal 8.0.x and will be removed before Drupal 9.0.0. Use \Drupal\Core\Database\Database::getConnection()->schema()->dropTable() instead. See https://www.drupal.org/node/2987737
+   */
+  public function testDbDropTable() {
+    $this->assertFalse(db_drop_table('temp_test_table'));
+  }
+
+}

core/tests/Drupal/KernelTests/Core/Database/RegressionTest.php

@@ -2,8 +2,6 @@
 
 namespace Drupal\KernelTests\Core\Database;
 
-use Drupal\Core\Database\Database;
-
 /**
  * Regression tests cases for the database layer.
  *
@@ -37,14 +35,10 @@ public function testRegression_310447() {
 
   /**
    * Tests the db_table_exists() function.
-   *
-   * @group legacy
-   *
-   * @expectedDeprecation db_table_exists() is deprecated in Drupal 8.0.x and will be removed before Drupal 9.0.0. Use $injected_database->schema()->tableExists($table) instead. See https://www.drupal.org/node/2947929.
    */
   public function testDBTableExists() {
-    $this->assertSame(TRUE, db_table_exists('test'), 'Returns true for existent table.');
-    $this->assertSame(FALSE, db_table_exists('nosuchtable'), 'Returns false for nonexistent table.');
+    $this->assertSame(TRUE, $this->connection->schema()->tableExists('test'), 'Returns true for existent table.');
+    $this->assertSame(FALSE, $this->connection->schema()->tableExists('nosuchtable'), 'Returns false for nonexistent table.');
   }
 
   /**
@@ -63,27 +57,4 @@ public function testDBIndexExists() {
     $this->assertSame(FALSE, db_index_exists('test', 'nosuchindex'), 'Returns false for nonexistent index.');
   }
 
-  /**
-   * Tests the db_set_active() function.
-   *
-   * @group legacy
-   *
-   * @expectedDeprecation db_set_active() is deprecated in Drupal 8.0.x and will be removed before Drupal 9.0.0. Use \Drupal\Core\Database\Database::setActiveConnection() instead. See https://www.drupal.org/node/2944084.
-   */
-  public function testDBIsActive() {
-    $get_active_db = Database::getConnection()->getKey();
-    $this->assert(db_set_active($get_active_db), 'Database connection is active');
-  }
-
-  /**
-   * Tests the db_drop_table() function.
-   *
-   * @group legacy
-   *
-   * @expectedDeprecation db_drop_table() is deprecated in Drupal 8.0.x and will be removed before Drupal 9.0.0. Use \Drupal\Core\Database\Database::getConnection()->schema()->dropTable() instead. See https://www.drupal.org/node/2987737
-   */
-  public function testDbDropTable() {
-    $this->assertFalse(db_drop_table('temp_test_table'));
-  }
-
 }